Gated? Power Amplifier

There is a simple industry-standard way to deal with this issue, and it's NOT at the high-voltage output. Think about it.

noise

btw.

Were transmitting a PSK signal at 75Khz. We can't tolerate any noise being transmitted during off periods, and my thinking was that shorting the input would not suffice. But you're probably right, any noise transmitted will be below any ambient noise. But, if I did need to switch on and off an AC signal of +- 100V, what would be the best way to do it? Some of our power amplifiers are noisy. Thanks for the replies. Vic

Awww - and I was going to tell him how to do it ! Have to wait til he's thought now. ;-)

Graham

It's hard *not* to make a power amp with 100dB or better signal to noise ratio. Isn't shorting the input good enough ?

What's the approx frequency spectrum of the signal to be transmitted btw.

Graham

How much distortion can you stand? Life is easier if you can withstand a little distortion in the signal.

If you have an existing amplifier, you can provide some isolation by just putting a pair of diodes in the path. When there is no current flowing in them, their impedance will be many K.

If I had to do it, and didn't have any way to look up a better way, I'd just bias both output devices off, in effect making it a tri-state output.

Hope this is close! Rich

Please enlighten those of us who are not involved in this kind of application and who just read here to learn.

Thanks, bob

Ahhh, if you're working from an old design it may not be so simple.

One excellent way to 'turn the amp off' is simply to control the circuit's bias generator(s). Often just removing current from the first stage will effectively put the amplifer output in a high-Z condition.

You need to be aware that it's high-Z this way though. Shorting the input gives a low-Z output which may be preferable depending on the transducer.

Graham