How to amplify 20 mv DC to 1-5 volts?

[radiofish]

I need to amplify a VSWR telemetry output coming from a transmitter that is about 20mV DC when the transmitter at full output (VSWR <1.1:1). The telemetry voltage ranges from zero (actually slightly negative) when there is no transmitter power output (no VSWR) and climbs to about 20mV when at full output. I would like to amplify this signal to about 2 volts (maybe 1-5 volts) so it can be detected by a remote interface on an exciter that drives this transmitter (designed to lower exciter drive when VSWR of the transmitter crosses a threshold).

Is there something available that does this or is there a simple design that involves a transistor, 5volt DC power supply, etc., that could be built from Radio Shack parts? Would a voltage regulator be needed in the circuit to keep the gain of the amplifier at a constant rate?

My Sine Systems remote telemetry can detect these low levels, but the exciter cannot so I’m unable to calibrate this threshold point on the exciter.

 

[tpt]

Definitely use a regulated supply for stability.

A Google search will probably bring up some schmeatics (try "DC amplifier schematic?" I've found some good information posted by various University courses.

Probably will use some exotic transistor they claim is common, but you can then go to the NTE sight to find specs and equiivalency, then get parts from Mouser or similar supplier. Radio Schack doesn't have much anymore.

 

[SamBuca]

> Probably will use some exotic transistor they claim is
> common, but you can then go to the NTE sight to find specs
> and equiivalency, then get parts from Mouser or similar
> supplier. Radio Schack doesn't have much anymore.

Radioshack has been one big disappointment within the last few years. But if you want to buy a cell phone, a cheap toy musical keyboard or get directv, they're your place.<P ID="signature">______________
</P>

 

[HOMEYD]

> I need to amplify a VSWR telemetry output coming from a
> transmitter that is about 20mV DC when the transmitter at
> full output (VSWR
>

Why not just use a simple op amp configered
for a gain of 100.

 

[rbrucecarter]

> I need to amplify a VSWR telemetry output coming from a
> transmitter that is about 20mV DC when the transmitter at
> full output (VSWR

Doing that in a single transistor is going to be problematic. I would do it with a single op amp. You can do any combination of gain and offset in a single op amp by downloading the following free program:

http://www.ti.com/opamppro

Enter your high and low input voltages (even negative), your high and low output voltages, and it will show you the schematic. You can select the op amp type, and run simulations to be sure it is stable. You can order free samples of whatever op amp you choose.

 

[vetguy]

Don't know if they still make it, but Moseley used to sell a DC amp that did exactly what you need. It was sold as an accessory to their remote control systems. May be able to find one used somewhere. I think it may have been a DCA-1.