Transistor gain, what if there is not enough current?What is “pull the collector below ground” and saturationBJT at saturationTransistor not supply enough currentIs the current gain value constant for a single BJT ?decreasing base current on saturated npn transistorCurrent flow in a BJT transistorTransistor power dissipation, current, and voltageconfused about pnp transistor current flowWhat are the real world limitations of using a transistor as a switch?Does a transistor reduce current flow?
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Transistor gain, what if there is not enough current?
What is “pull the collector below ground” and saturationBJT at saturationTransistor not supply enough currentIs the current gain value constant for a single BJT ?decreasing base current on saturated npn transistorCurrent flow in a BJT transistorTransistor power dissipation, current, and voltageconfused about pnp transistor current flowWhat are the real world limitations of using a transistor as a switch?Does a transistor reduce current flow?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
But what if there is a resistor that reduces current?
So let's say there is 1mA between base and emitter and a gain of 100x that means there will be 100mA between collector and emitter?
But what if there is a 5v supply voltage and a 1000ohm resistor between supply and collector, it will be impossible for this much current to flow.
transistors
asked May 5 at 22:58
user221241user221241
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
But what if there is a resistor that reduces current?
So let's say there is 1mA between base and emitter and a gain of 100x that means there will be 100mA between collector and emitter?
But what if there is a 5v supply voltage and a 1000ohm resistor between supply and collector, it will be impossible for this much current to flow.
transistors
asked May 5 at 22:58
user221241user221241
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
7
$begingroup$
That mode of operation is : saturation.
$endgroup$
– analogsystemsrf
May 5 at 23:23
$begingroup$
You typically duplicate the setup a few million times, invent a whole new branch of using electronics and port Doom to the result.
$endgroup$
– DonFusili
2 days ago
$begingroup$
For bipolar transistors (BJT) it is called saturation mode, but just be aware that for field-effect transistors (FET) the saturation mode means almost exactly the opposite.
$endgroup$
– jpa
2 days ago
add a comment |
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
But what if there is a resistor that reduces current?
So let's say there is 1mA between base and emitter and a gain of 100x that means there will be 100mA between collector and emitter?
But what if there is a 5v supply voltage and a 1000ohm resistor between supply and collector, it will be impossible for this much current to flow.
transistors
asked May 5 at 22:58
user221241user221241
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
But what if there is a resistor that reduces current?
So let's say there is 1mA between base and emitter and a gain of 100x that means there will be 100mA between collector and emitter?
But what if there is a 5v supply voltage and a 1000ohm resistor between supply and collector, it will be impossible for this much current to flow.
transistors
transistors
asked May 5 at 22:58
user221241user221241
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked May 5 at 22:58
user221241user221241
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked May 5 at 22:58
user221241user221241
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked May 5 at 22:58
user221241user221241
355
asked May 5 at 22:58
user221241user221241
355
355
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
user221241 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
7
$begingroup$
That mode of operation is : saturation.
$endgroup$
– analogsystemsrf
May 5 at 23:23
$begingroup$
You typically duplicate the setup a few million times, invent a whole new branch of using electronics and port Doom to the result.
$endgroup$
– DonFusili
2 days ago
$begingroup$
For bipolar transistors (BJT) it is called saturation mode, but just be aware that for field-effect transistors (FET) the saturation mode means almost exactly the opposite.
$endgroup$
– jpa
2 days ago
add a comment |
7
$begingroup$
That mode of operation is : saturation.
$endgroup$
– analogsystemsrf
May 5 at 23:23
$begingroup$
You typically duplicate the setup a few million times, invent a whole new branch of using electronics and port Doom to the result.
$endgroup$
– DonFusili
2 days ago
$begingroup$
For bipolar transistors (BJT) it is called saturation mode, but just be aware that for field-effect transistors (FET) the saturation mode means almost exactly the opposite.
$endgroup$
– jpa
2 days ago
7
7
$begingroup$
That mode of operation is : saturation.
$endgroup$
– analogsystemsrf
May 5 at 23:23
$begingroup$
That mode of operation is : saturation.
$endgroup$
– analogsystemsrf
May 5 at 23:23
$begingroup$
You typically duplicate the setup a few million times, invent a whole new branch of using electronics and port Doom to the result.
$endgroup$
– DonFusili
2 days ago
$begingroup$
You typically duplicate the setup a few million times, invent a whole new branch of using electronics and port Doom to the result.
$endgroup$
– DonFusili
2 days ago
$begingroup$
For bipolar transistors (BJT) it is called saturation mode, but just be aware that for field-effect transistors (FET) the saturation mode means almost exactly the opposite.
$endgroup$
– jpa
2 days ago
$begingroup$
For bipolar transistors (BJT) it is called saturation mode, but just be aware that for field-effect transistors (FET) the saturation mode means almost exactly the opposite.
$endgroup$
– jpa
2 days ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
Good.
But what if there is a resistor that reduces current?
Then the transistor will drive into saturation.
There are many times when this is useful - most notably in the NPN low-side switch. Here we want the transistor to behave like a switch so we inject a base current high enough to ensure that the transistor saturates so that the collector-emitter voltage, VCE is as low as possible. This eliminates variation in load current due to variations in the transistor gain and also ensures that power dissipation in the transistor is at a minimum.
Figure 1. A typical NPN low-side switch can be driven into saturation by making R1 low enough. Source: LEDnique by the author.
To ensure saturation it is normal to assume a much lower current gain than the hfe paramater might suggest. 10 to 20 is typical. See the linked article for a worked calculation.
answered May 5 at 23:38
TransistorTransistor
90.9k788195
$endgroup$
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
add a comment |
$begingroup$
The purpose of biasing a transistor amplifier is to make sure that this problem does not occur. The resistor values are selected so that without any input signal (other than the dc bias) the output voltage will be about half way between ground and Vcc. That setup allows for the largest possible linear amplification.
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
$endgroup$
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
Good.
But what if there is a resistor that reduces current?
Then the transistor will drive into saturation.
There are many times when this is useful - most notably in the NPN low-side switch. Here we want the transistor to behave like a switch so we inject a base current high enough to ensure that the transistor saturates so that the collector-emitter voltage, VCE is as low as possible. This eliminates variation in load current due to variations in the transistor gain and also ensures that power dissipation in the transistor is at a minimum.
Figure 1. A typical NPN low-side switch can be driven into saturation by making R1 low enough. Source: LEDnique by the author.
To ensure saturation it is normal to assume a much lower current gain than the hfe paramater might suggest. 10 to 20 is typical. See the linked article for a worked calculation.
answered May 5 at 23:38
TransistorTransistor
90.9k788195
$endgroup$
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
add a comment |
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
Good.
But what if there is a resistor that reduces current?
Then the transistor will drive into saturation.
There are many times when this is useful - most notably in the NPN low-side switch. Here we want the transistor to behave like a switch so we inject a base current high enough to ensure that the transistor saturates so that the collector-emitter voltage, VCE is as low as possible. This eliminates variation in load current due to variations in the transistor gain and also ensures that power dissipation in the transistor is at a minimum.
Figure 1. A typical NPN low-side switch can be driven into saturation by making R1 low enough. Source: LEDnique by the author.
To ensure saturation it is normal to assume a much lower current gain than the hfe paramater might suggest. 10 to 20 is typical. See the linked article for a worked calculation.
answered May 5 at 23:38
TransistorTransistor
90.9k788195
$endgroup$
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
add a comment |
$begingroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
Good.
But what if there is a resistor that reduces current?
Then the transistor will drive into saturation.
There are many times when this is useful - most notably in the NPN low-side switch. Here we want the transistor to behave like a switch so we inject a base current high enough to ensure that the transistor saturates so that the collector-emitter voltage, VCE is as low as possible. This eliminates variation in load current due to variations in the transistor gain and also ensures that power dissipation in the transistor is at a minimum.
Figure 1. A typical NPN low-side switch can be driven into saturation by making R1 low enough. Source: LEDnique by the author.
To ensure saturation it is normal to assume a much lower current gain than the hfe paramater might suggest. 10 to 20 is typical. See the linked article for a worked calculation.
answered May 5 at 23:38
TransistorTransistor
90.9k788195
$endgroup$
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.
Good.
But what if there is a resistor that reduces current?
Then the transistor will drive into saturation.
There are many times when this is useful - most notably in the NPN low-side switch. Here we want the transistor to behave like a switch so we inject a base current high enough to ensure that the transistor saturates so that the collector-emitter voltage, VCE is as low as possible. This eliminates variation in load current due to variations in the transistor gain and also ensures that power dissipation in the transistor is at a minimum.
Figure 1. A typical NPN low-side switch can be driven into saturation by making R1 low enough. Source: LEDnique by the author.
To ensure saturation it is normal to assume a much lower current gain than the hfe paramater might suggest. 10 to 20 is typical. See the linked article for a worked calculation.
answered May 5 at 23:38
TransistorTransistor
90.9k788195
answered May 5 at 23:38
TransistorTransistor
90.9k788195
answered May 5 at 23:38
TransistorTransistor
90.9k788195
answered May 5 at 23:38
TransistorTransistor
90.9k788195
90.9k788195
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
add a comment |
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
Will the b -> e current be reduced if the c -> e current is reduced?
$endgroup$
– user221241
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
No. The $ I_be $ current is determined by R1 and $ V_be $ of the transistor. It doesn't "know" about the collector current.
$endgroup$
– Transistor
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
So the "beta" for the transistor only holds when R1 and R2 are within certain values?
$endgroup$
– user221241
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
See if the discussion on Physics Forums helps.
$endgroup$
– Transistor
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
$begingroup$
@user221241 β only applies when the transistor is in forward-active mode. The relevant characteristic for saturation mode is called the saturation voltage, Vce,sat.
$endgroup$
– Hearth
2 days ago
add a comment |
$begingroup$
The purpose of biasing a transistor amplifier is to make sure that this problem does not occur. The resistor values are selected so that without any input signal (other than the dc bias) the output voltage will be about half way between ground and Vcc. That setup allows for the largest possible linear amplification.
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
$endgroup$
add a comment |
$begingroup$
The purpose of biasing a transistor amplifier is to make sure that this problem does not occur. The resistor values are selected so that without any input signal (other than the dc bias) the output voltage will be about half way between ground and Vcc. That setup allows for the largest possible linear amplification.
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
$endgroup$
add a comment |
$begingroup$
The purpose of biasing a transistor amplifier is to make sure that this problem does not occur. The resistor values are selected so that without any input signal (other than the dc bias) the output voltage will be about half way between ground and Vcc. That setup allows for the largest possible linear amplification.
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
$endgroup$
The purpose of biasing a transistor amplifier is to make sure that this problem does not occur. The resistor values are selected so that without any input signal (other than the dc bias) the output voltage will be about half way between ground and Vcc. That setup allows for the largest possible linear amplification.
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
answered May 5 at 23:01
Elliot AldersonElliot Alderson
8,39921122
8,39921122
add a comment |
add a comment |
user221241 is a new contributor. Be nice, and check out our Code of Conduct.
user221241 is a new contributor. Be nice, and check out our Code of Conduct.
user221241 is a new contributor. Be nice, and check out our Code of Conduct.
user221241 is a new contributor. Be nice, and check out our Code of Conduct.
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7
$begingroup$
That mode of operation is : saturation.
$endgroup$
– analogsystemsrf
May 5 at 23:23
$begingroup$
You typically duplicate the setup a few million times, invent a whole new branch of using electronics and port Doom to the result.
$endgroup$
– DonFusili
2 days ago
$begingroup$
For bipolar transistors (BJT) it is called saturation mode, but just be aware that for field-effect transistors (FET) the saturation mode means almost exactly the opposite.
$endgroup$
– jpa
2 days ago