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'[EE]: need simple amplifier circuit'
2005\12\29@144441 by John Waters

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Hi All,

I need to apply a signal on a load regularly. The load is a coil with an
impedence of 60 ohms. The requirement of the signal is 60 Hz, sinewave,
around 12 v p-p (as measured across the load during operation). Is there any
simple amplifier circuit with one or two transistors that can do the job? I
can feed a small amplitude adjustable 60Hz input to the circuit using a
singnal generator.

Thanks in advance!

John


2005\12\29@150723 by Mark Scoville

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face
> I need to apply a signal on a load regularly. The load is a coil with an
> impedence of 60 ohms. The requirement of the signal is 60 Hz, sinewave,
> around 12 v p-p (as measured across the load during operation).
> Is there any
> simple amplifier circuit with one or two transistors that can do
> the job? I
> can feed a small amplitude adjustable 60Hz input to the circuit using a
> singnal generator.


How about just using a transformer? (assuming you live where 60Hz is the
power freq). If you need 12V p-p *exactly* then run the transformer from a
variac and adjust as needed.

-- Mark



2005\12\29@152731 by Mark Rages

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On 12/29/05, John Waters <spam_OUTjohn_fm_watersTakeThisOuTspamhotmail.com> wrote:
> Hi All,
>
> I need to apply a signal on a load regularly. The load is a coil with an
> impedence of 60 ohms. The requirement of the signal is 60 Hz, sinewave,
> around 12 v p-p (as measured across the load during operation). Is there any
> simple amplifier circuit with one or two transistors that can do the job? I
> can feed a small amplitude adjustable 60Hz input to the circuit using a
> singnal generator.
>
> Thanks in advance!
>
> John
>

What power supply do you have available?  I seem to remember 12 VDC
from your other post.

Do you have control over both ends of this coil, or is one end tied to ground?

If you have control of both end of the coil, you can use a bridge-tied
car audio power amplifier IC, such as two TDA2003s in a bridge
configuration.

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2005\12\29@160455 by Mark Rages

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On 12/29/05, Mark Rages <.....markragesKILLspamspam@spam@gmail.com> wrote:
> If you have control of both end of the coil, you can use a bridge-tied
> car audio power amplifier IC, such as two TDA2003s in a bridge
> configuration.

Replying to myself.  A single TDA2005 would be simpler / cheaper.

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2005\12\29@164052 by Spehro Pefhany

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At 11:44 AM 12/29/2005 -0800, you wrote:
>Hi All,
>
>I need to apply a signal on a load regularly. The load is a coil with an
>impedence of 60 ohms. The requirement of the signal is 60 Hz, sinewave,
>around 12 v p-p (as measured across the load during operation). Is there any
>simple amplifier circuit with one or two transistors that can do the job? I
>can feed a small amplitude adjustable 60Hz input to the circuit using a
>singnal generator.
>
>Thanks in advance!
>
>John

How much distortion and DC offset can you tolerate? A simple op-amp with
emitter-follower boosters comes to mind, but you'll get crossover distortion
(where the op-amp output would otherwise have to slew 1200mV instantly)
even at
60Hz, unless they are biased, which takes a few more parts. It won't be
short-circuit protected either. You might be able to get away with TO-92
transistors, depending on the power supply voltages (if it is 12V P-P = 6V
peak
= 4.2V RMS. If the 60 ohms is resistive, that's only 300mW actual output
power.
Do a search for "Class AB" amplifier circuits. I suggest a DC-coupled circuit
at the output since the output coupling capacitor would otherwise be fairly
large
for such a low frequency. You'll need + and - supply rails.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
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2005\12\30@150330 by Peter

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On Thu, 29 Dec 2005, John Waters wrote:

{Quote hidden}

Any audio amp. If the signal generator can make 12Vpp then all you need
is a PNP+NPN emitter follower with its bias circuit (that is the end
stange of any transistor audio amp)

Peter

2005\12\30@150458 by Peter

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More: You probably want to implement kickback absorption or prevention.
Absorption means clamping diodes or zeners and/or RC group, and
prebention means starting the signal on a zero crossing and stopping it
on zero current (a optotriac in series with the output can help).

Peter

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