Opamp power supply

Hi all, I'm about to build this detector/audio amp circuit.

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I want to run it from batteries, I thought it was +/- 4.4v supply. I thought I was going to use 6 AA cells and center tap them,

but maybe not. I just noticed it looks like it's +12 and -4.4v. First, does that make sense? Or could it be an error in the presentation. See figure 2 and 1 for Power supply connections.

Any other thoughts about the circuit?

Thanks, Mikek

Reply to
amdx
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Looks like a great noise generator.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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Reply to
John Larkin

I'm not surprised to hear a negative critique. I built the amp he designed, and when I had a question, I got all kinds of remarks about what was wrong with it and that it didn't meet his specs.

Ok, so what would you do different for the detector? All I want to do is drive a meter to compare ferrite L/C antennas. Since I have a high impedance amp with 50 ohms out, I could use a low input impedance detector. But either way.

550kHz to 1700kHz range needed, wider is better.

The audio part is a useful bonus.

Mikek

Reply to
amdx

Opamp driving a transformer... very 70s. IC used to generate -ve rail when the input could just have been divided or rectified both ways... why?

NT

Reply to
tabbypurr

I'd hook your antenna directly to an oscilloscope. Maybe with a jfet follower if you care much about capacitive loading.

Reply to
John Larkin

I plan on using the Radio Shack 1000 ohm to 8 ohm transformer, I think I have one around here.

I don't know, post a quick schematic so I can see what you mean.

Thanks, Mikek

Reply to
amdx

Is that from the opamp or the circuit design?

Reply to
amdx

I want it battery operated, so I can setup in the backyard away from noise sources and read an analog meter. I'd like as little loading as possible which I think I have, with the Kleijer amp I previously built. This can be my impedance converter very high input to 50 ohms output.

Thanks, Mikek

Reply to
amdx

the former: o----------Reg------o +out | | dc in +-------o 0v | | o----------Reg------o -out

the latter, from ac in:

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Bottom left for half wave version

But if you're running from battery, why not just tap the battery? It's a fair few cells, but they'll last longer due to lower current draw.

NT

Reply to
tabbypurr

A front-end diode rectifier, a crystal set, will be a very nonlinear detector, with a bad temperature coefficient. You might amplify up to some decent signal level, and then rectify. Pop in attenuators as needed.

Several people make really cool integrated, wide-range, log-output RF detector chips, with all the hard work done. ADI, LTC, maybe TI. Talk someone out of an eval board.

Reply to
John Larkin

That can't work, of course; the third pin of a regulator (the ones connected and labeled "0v") is not driven to any particular voltage level. It's a power supply and voltage SENSE pin, not a driven output. You might get by with a resistor and two zener diodes, if you really NEED regulation. Op amps work fine on filtered, unregulated power.

Reply to
whit3rd

Interesting little IC - TO92, complete TRF AM radio:

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Grizzly H.
Reply to
mixed nuts

The opamp and the megohm input resistors.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

Oh, cause I think he's using a wall wart. Which limited his thinking.

I think it is +12V and -4.4V supplies, he had 12V from the wall wart, then just developed the -4.4V. Just a guess.

Reply to
amdx

You put reservoir caps on the output, and zeners on each rail to take care of too much imbalance. Crude but effective. It works.

NT

Reply to
tabbypurr

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