Is a Zobel network needed here?

Thread Starter

Yabba Rays

Joined Oct 5, 2016
19
I understand that a Zobel network is added at the o/p of an audio amp to retain stability into the inductive load of the loudspeaker.
A TDA2040 amp is used here to modulate a 5 watt AM transmitter. Is the load inductive enough to suggest that a Zobel network is required? I doubt it will do any harm if added, but just wondered if it *should* be added.

(L4 is about 1 mH.)

Thanks.

Janet
 

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Thread Starter

Yabba Rays

Joined Oct 5, 2016
19
Add the Zobel network so that the amplifier has a load at high frequencies. A speaker's inductance causes its impedance to be too high at high frequencies).
The opamp's negative feedback is wrong:
Thank you for the correction. That design always had a poor reputation. There was a circuit board sold, but I don't know if it had the same error.

There is no loudspeaker, the load is the RFC and FET, but you suggest a Zobel network is still required.

Thanks,

Janet
 

Audioguru again

Joined Oct 21, 2019
1,262
I mentioned the loudspeaker because the amplifier oscillates when it has a high load impedance. The loudspeaker 's inductance causes its impedance to be high at high frequencies, therefore the amplifier needs a Zobel network when its load impedance is high, like on your circuit..
 
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