Hi,
I've been thinking on building a class AB amp for my Full range speakers with the following criterion:
1) No global feedback. Apparently High efficiency full range speakers tend to dislike global feedback. probably because it results in a much higher damping factor.
2) High quiescent current for low power class A operation.
3) Low power (5 to 10W) is probably enough.
4 ) Reasonable distortion levels (< 0.2%)
5) Fixed supply voltage.
6) Minimum number of stages.
7) Single supply operation as I intend to power it from a power brick.
Of course the easiest starting point would be the traditional 3 transistor with 2 diode for biasing as in the attachment. To push the circuit deeper into class A territory I will use 3 diodes and additional resistor resistor at the emitter.
However a quick analysis will show it is not a very viable circuit.
1) The driver will not have enough current to drive the output transistor at high voltage swings.
There are many ways it can be solved:
1) darlington TIP120 for the output transistors
2) Sziklai Pair
3) or a beefier driver stage with higher bias current by using smaller value resistors. However that will result in very low input impedance, so might have to use a mosfet or Jfet to drive the transistors.
4) Use a voltage follower for the driver stage and an additional gain stage.
I would like you opinion which do you think is the best solution.
Other than that would appreciate any comments of how this can circuit can be improved?
1) Zener regulator for the driver stage?
2) resistor and large cap power supply bypass for the driver stage?
Thanking all in advance.
Oon
I've been thinking on building a class AB amp for my Full range speakers with the following criterion:
1) No global feedback. Apparently High efficiency full range speakers tend to dislike global feedback. probably because it results in a much higher damping factor.
2) High quiescent current for low power class A operation.
3) Low power (5 to 10W) is probably enough.
4 ) Reasonable distortion levels (< 0.2%)
5) Fixed supply voltage.
6) Minimum number of stages.
7) Single supply operation as I intend to power it from a power brick.
Of course the easiest starting point would be the traditional 3 transistor with 2 diode for biasing as in the attachment. To push the circuit deeper into class A territory I will use 3 diodes and additional resistor resistor at the emitter.
However a quick analysis will show it is not a very viable circuit.
1) The driver will not have enough current to drive the output transistor at high voltage swings.
There are many ways it can be solved:
1) darlington TIP120 for the output transistors
2) Sziklai Pair
3) or a beefier driver stage with higher bias current by using smaller value resistors. However that will result in very low input impedance, so might have to use a mosfet or Jfet to drive the transistors.
4) Use a voltage follower for the driver stage and an additional gain stage.
I would like you opinion which do you think is the best solution.
Other than that would appreciate any comments of how this can circuit can be improved?
1) Zener regulator for the driver stage?
2) resistor and large cap power supply bypass for the driver stage?
Thanking all in advance.
Oon