DC offset Amp.

Thread Starter

sas pinkie

Joined Nov 6, 2008
1
Hi guys,

I am a transmitter engineer, and have a bit of a problem. I need to build a test jig for an audio card out of one of the transmitters here on site that is offering some trouble.

I need to generate audio ( I am using a test tone genorator on a sine wave for this) that is 6v Pk - Pk (I have a basic amp to provide this amplitude).... but, and here is where I am stuck, it needs to be at a + offset of 6.2v so max Voltage is +9.2V, and minimum voltage is 3.2V.

I thought of building a basic amp using perhaps an off the shelf op amp like the 351, and changing the feed back to generate the off set. Any ideas on how to alter the feed back loop to create the of set that I am looking for? or any other suggestions to achieve the results, would be greatly appreciated.

Cheers.....
 

KL7AJ

Joined Nov 4, 2008
2,208
Hi guys,

I am a transmitter engineer, and have a bit of a problem. I need to build a test jig for an audio card out of one of the transmitters here on site that is offering some trouble.

I need to generate audio ( I am using a test tone genorator on a sine wave for this) that is 6v Pk - Pk (I have a basic amp to provide this amplitude).... but, and here is where I am stuck, it needs to be at a + offset of 6.2v so max Voltage is +9.2V, and minimum voltage is 3.2V.

I thought of building a basic amp using perhaps an off the shelf op amp like the 351, and changing the feed back to generate the off set. Any ideas on how to alter the feed back loop to create the of set that I am looking for? or any other suggestions to achieve the results, would be greatly appreciated.

Cheers.....
Great to have another R.F. engineer around here, Sas! I've been crawling around inside high power broadcast transmitters for 35 years. Also spent a lot of time at HAARP. http://www.haarp.alaska.edu


Why not just create a voltage dividier across a power supply and couple your audio through a capacitor to the junction of the resistors?

Eric
 

SgtWookie

Joined Jul 17, 2007
22,201
Eric's idea will work just great if you have a high Z load.

If your load is lower Z, you could use an LF351, TL071 or similar as a buffer.
 

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