| Electronics > Beginners |
| Class B Amp |
| (1/2) > >> |
| Steve1959:
I was taught that a class b amp (transistors) is usually in a push-pull configuration. Therefore requiring two. I have a circuit for a transistor demodulator for AM and it says it is wired for class B. Can a single transistor be wired class B or is it a typo? Find attached a .jpg to see the circuit. My very first post ever. |
| hamster_nz:
Looks to be typo. That is a common emitter amplifier. Unless something funny is going on and the transistor is biased to cause non-linear operation. |
| Calvin:
Hi, --- Quote ---Can a single transistor be wired class B or is it a typo? --- End quote --- A single transistor can be biased in class B (or class A and C) however You wish. The classification only describes over how much part of 360° of a phase the transistor conducts. Class B is defined as 180°, class A as 180° to 360°, class C 0° to 180°. In this case however it seems rather a typo, as it wouldn´t make much sense to bias this amplifier below class A regards Calvin |
| Gyro:
It's hard to tell without component values but the placement of C2 is unusual. In combination with R3 this will form a time constant which will limit the rate of rise of the output when Q1's Base is being driven low by the input waveform. When the Base is driven high, it will form a lower resistance path for charging C2 again. It would be wrong to describe it as Class-B amplifier though as there's always going to be some C-E current flowing through Q1, even if it varies a lot more than usual for a common emitter stage (again, depending on component values). |
| mikerj:
I suspect this really is class B (or very close to) as the biasing resistors will be set to barely turn on the transistor. It's effectively a half wave rectifier with some gain and close to zero forward voltage due to the biasing. |
| Navigation |
| Message Index |
| Next page |