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Gated? Power Amplifier

Hi,
I would be grateful for some ideas on how to best switch the output of
a power amplifier ON for the transmission of a waveform burst
(underwater ping) then OFF (approximately 1 second pulse repetition
frequency, 5-10 ms pulse duration). The output will be +- 100 Volt
peak-to-peak. To prevent quiesent noise during the off time, we want
the amplifier disconnected from the load. The waveform will be
generated by an Arbitrary Waveform Generator.

We don't want to use mechanical relays for reliability and bounce
issues.

Thanks in advance for any ideas!

Any proper terminology for this application, and/or applicable
semiconductor devices to use would also be helpful to facilitate my
internet research.
Victor
 
W

Winfield Hill

Jan 1, 1970
0
[email protected] wrote...
I would be grateful for some ideas on how to best switch the output
of a power amplifier ON for the transmission of a waveform burst
(underwater ping) then OFF (approximately 1 second pulse repetition
frequency, 5-10 ms pulse duration). The output will be +- 100 Volt
peak-to-peak. To prevent quiesent noise during the off time, we
want the amplifier disconnected from the load. The waveform will
be generated by an Arbitrary Waveform Generator.

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

Pooh Bear

Jan 1, 1970
0
Winfield said:
[email protected] wrote...

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

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

Graham
 
P

Pooh Bear

Jan 1, 1970
0
To prevent quiesent noise during the off time, we want
the amplifier disconnected from the load.

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
 
S

schmoester

Jan 1, 1970
0
Pooh said:
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

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
 
K

Ken Smith

Jan 1, 1970
0
Hi,
I would be grateful for some ideas on how to best switch the output of
a power amplifier ON for the transmission of a waveform burst
(underwater ping) then OFF (approximately 1 second pulse repetition
frequency, 5-10 ms pulse duration). The output will be +- 100 Volt
peak-to-peak. To prevent quiesent noise during the off time, we want
the amplifier disconnected from the load. The waveform will be
generated by an Arbitrary Waveform Generator.

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.
 
R

Robert Latest

Jan 1, 1970
0
On 19 May 2005 13:22:07 -0700,
Winfield Hill said:
[email protected] wrote...

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

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

Thanks,
bob
 
P

Pooh Bear

Jan 1, 1970
0
schmoester said:
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.

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
 
R

Rich Grise

Jan 1, 1970
0
On 19 May 2005 13:22:07 -0700,


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

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
 
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