Electronic – Is it possible to suppress oscillation at reactive load (non inverting amp)

non-invertingpiezotransducer

I am using a non inverting amp with B class voltage follower to drive a piezoelectric transducer (used as sonar for fish scanning in boats). I am using trains of 20 sinewave pulses (85KHz), like the ones you can see in the blue image (input).

enter image description here

However, at the output I am getting the green signal, which have undesired residual oscillations with the same frequency. The problem with this, is that the receiver circuit amplify the full incoming wave with a large gain – and there is no way to difference the 20 pulses from the "blank" space. This jamming effect is screwing up the data transmission.

The circuit I build in PCB is this:

enter image description here

I have discovered in simulation that if I decrease the value of the decoupling capacitor, in theory the oscillation tale dissapears. I will try this in the real circuit, but I would like to know which is the correct way to deal with this.

BTW, these parasitic oscillation just happens when the transducer is plugged in the circuit. I am pretty sure isnt related to the operational amplifier.

Best Answer

your output stage has 1.2V of dead-band so when the signal stops it's not driving the output to fixed voltage and so the transducer model continues to ring.

change the output stage to be class AB instead.

or replace C1 with a wire and take the feedback (R4) from Q1 base instead of from U1 output