Need a simple amplifier

[bnfdvn]

I need to amplify a 1 volt (p-p) sine wave to a 15-25 volt (p-p) sine wave to drive a 220 Ohm load. The frequencies are audio range (<20 KHz). Any suggestions as a starting point would be appreciated.

 

[Nigel Goodwin]

What is the actual application?, it sounds a bit weird?.

But a suitable opamp 'may' be able to do that, if not, an opamp with a pair of output transistors would.

 

[bnfdvn]

I am making a circuit to simulate a magnetic pickup off the teeth of a flywheel. I have the signal developed and the voltage level is 1 volt. I need to kick this up to 20 (or so) volts for the receiving device. I have + and - 15 VDC power supply, along with 24 VDC power supply.

 

[Nigel Goodwin]

It's the receivng device which is the important bit - why has it got a 220 ohm input? (if indeed it has).

 

[bnfdvn]

I can't tell you why the input impedance is 220 Ohms. I just re-checked the manufacturer's specs and it is indeed 220 Ohms.

 

[Nigel Goodwin]

I can't tell you why the input impedance is 220 Ohms. I just re-checked the manufacturer's specs and it is indeed 220 Ohms.

And what is this normally fed from (you're been very obscure).

 

[bnfdvn]

I just took the receiving device (generator controller) apart and the terminals for the magnetic pickup (that I am trying to simulate) go to a transformer. The manufacturer's data for troubleshooting the generator controller says that the impedance of the input terminals should be around 220 Ohms. Indeed, when I put an Ohmmeter on the input terminals, the impedance is 223.4 Ohms. The magnetic pickup on the generator normally outputs up to 30 volts AC but less at lower generator speeds (startup, idle, etc.). I figure that with my power supplies, 20-25 VAC should be fine.

I have developed a 1 volt signal by programming a PIC to output a square wave and then running the square wave through some Op Amp integrators to make a sine wave, then through a AGC circuit to get a constant signal amplitude (since the integrator output signal level decreases with increasing frequency) and now to the final stage - amplifying the 1 volt signal from the AGC to the 20-25 Volt signal needed by the transformer on the generator controller.

What else would you like to know??

 

[Nigel Goodwin]

The fact it has a transformer on the input it what's vital - but measuring it with a meter measures the resistance, NOT the impedance, which will be higher - and will depend on the load on the output of the transformer, and it's turns ratio (so it's a bit complicated.

Like I said before, try an opamp with a couple of transistors on the output (and included in the feedback loop) - or first, try just an opamp and see how it works.

 

[CHELLIE]

It's the receivng device which is the important bit - why has it got a 220 ohm input? (if indeed it has).

Hi Nigel I think the coils resistance for the pick up coil may be 220 ohms, then it may generate a voltage from a Hall effect, a wire coil around a magnet then the making and breaking of a magnetic field from the teeth of a flywheel, interesting project so my guess is that he is trying to simulate a hall effect and have it regulated/adjustable

there might be some info on this page that might be of help.
https://books.google.com/books?id=_...wAw#v=onepage&q=simulated hall effect&f=false

 

[ronv]

If you could get by with 15 volts Try a lm386 audio amp. Cheap & dirty -- but easy.