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If your collector voltage is above the saturation region, the Hfe won't change much with collector voltage, so all you need is a resistor in the collector to measure the collector current and a resistor in the base circuit to measure the base current.
If your collector voltage is above the saturation region, the Hfe won't change much with collector voltage, so all you need is a resistor in the collector to measure the collector current and a resistor in the base circuit to measure the base current.
If your collector voltage is above the saturation region, the Hfe won't change much with collector voltage, so all you need is a resistor in the collector to measure the collector current and a resistor in the base circuit to measure the base current.
If your collector voltage is above the saturation region, the Hfe won't change much with collector voltage, so all you need is a resistor in the collector to measure the collector current and a resistor in the base circuit to measure the base current.
So, you need 3 or 4 A/Ds in the microcontroller to measure the base voltage, the base drive voltage, the collector voltage, and if the VCC is not fixed, a 4th A/D to measure VCC. Alternativly, you could use one A/D and switch the inputs.
So, you need 3 or 4 A/Ds in the microcontroller to measure the base voltage, the base drive voltage, the collector voltage, and if the VCC is not fixed, a 4th A/D to measure VCC. Alternativly, you could use one A/D and switch the inputs.
The classic way to measure gain is to measure only ONE parameter, the collector current. For your purposes it would be easier to measure the collector voltage, you can then easily calculate the current and hence the gain.
The technique is to feed the base from a constant current source, no need to measure it as you already know what it is.
So historically, you would feed the base via a constant current source, and have a milliammeter in the collector, by suitable selection of the constant base current and meter range, you can read the current gain directly off the analogue meter scale.
There are obviously far more complicated methods, but this is simple, easy to do, and should do all you need?.
Base drive voltage is the voltage supplying current to the base. It could be VCC which would reduce the number of measurments you have to make. Fixed VCC will simplify matters because you don't have to measure it with the micro.
The classic way to measure gain is to measure only ONE parameter, the collector current. For your purposes it would be easier to measure the collector voltage, you can then easily calculate the current and hence the gain.
The technique is to feed the base from a constant current source, no need to measure it as you already know what it is.
So historically, you would feed the base via a constant current source, and have a milliammeter in the collector, by suitable selection of the constant base current and meter range, you can read the current gain directly off the analogue meter scale.
There are obviously far more complicated methods, but this is simple, easy to do, and should do all you need?.
yes i think its a goo idea. i dont want to see the gain trough an anlaouge meter cause i need to determine if the gain of the tested transistor is bigger of smaller than a certain value.
The classic way to measure gain is to measure only ONE parameter, the collector current. For your purposes it would be easier to measure the collector voltage, you can then easily calculate the current and hence the gain.
The technique is to feed the base from a constant current source, no need to measure it as you already know what it is.
So historically, you would feed the base via a constant current source, and have a milliammeter in the collector, by suitable selection of the constant base current and meter range, you can read the current gain directly off the analogue meter scale.
There are obviously far more complicated methods, but this is simple, easy to do, and should do all you need?.
yes i think its a goo idea. i dont want to see the gain trough an anlaouge meter cause i need to determine if the gain of the tested transistor is bigger of smaller than a certain value.
The classic way to measure gain is to measure only ONE parameter, the collector current. For your purposes it would be easier to measure the collector voltage, you can then easily calculate the current and hence the gain.
The technique is to feed the base from a constant current source, no need to measure it as you already know what it is.
So historically, you would feed the base via a constant current source, and have a milliammeter in the collector, by suitable selection of the constant base current and meter range, you can read the current gain directly off the analogue meter scale.
There are obviously far more complicated methods, but this is simple, easy to do, and should do all you need?.
yes i think its a goo idea. i dont want to see the gain trough an anlaouge meter cause i need to determine if the gain of the tested transistor is bigger of smaller than a certain value.
Switch different resistor values, you probably don't require variable current, just a small switched selection of values.
If you do want fully variable?, you need to provide an analogue output, use either an R2R ladder, or PWM and filter - in both cases you will need to convert the voltage to a current.
Switch different resistor values, you probably don't require variable current, just a small switched selection of values.
If you do want fully variable?, you need to provide an analogue output, use either an R2R ladder, or PWM and filter - in both cases you will need to convert the voltage to a current.
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