Opamp wanted

"Bearplug Bearplug Bearplug"

Life will be short if you insist on that voltage.

The TL072 meets the spec you posted.

What do YOU imagine is so special about the " drive capability " of the

Audiophool bullshit aside.

.... Phil

Date: Mon, Sep 7, 2009, 8:37pm (PDT+17) From: phil snipped-for-privacy@tpg.com.au (Phil=A0Allison)

I see it routinely used. Don't know about mortality data. Anyhow, I'm trying to avoid the 5534/32. The opamp in this spot is a non-inverting buffer fed by a 50K pot. I'd like to not load down the pot, and avoid an input cap.

It'd be fine, except the 5534/32 is spec'd for 10V out into much lower loads. The one in question is a tone control network with about 1K input Z.

Adequate current drive for a nasty load. My audiophool instincts rule elsewhere.

Regards, b B.

TL071/072

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Quantify "nasty" for us.

I was rummaging around in my spare parts box and found a bunch of RCA HC2000 op amps.

Quantification will take a while, but this might qualify. The load is a complex network, not a straight resistance. The TLOxx chart shows adequate p-to-p voltage output at low loading, but I've noticed 5534/32 being preferred for driving cable. A bi-fet equivalent looked ideal.

A 7-amp device should drive the issue straight to Hell nicely.

On Mon, 07 Sep 2009 02:45:51 -0700, Bearplug Bearplug Bearplug wrote: Message-ID:

Holy Crap! There's still "Web-TV"??????

TL082?

Have Fun! Rich

Hmm, does the opa134 series go to +/-18V?

George H.

Buffer? Like, unity gain? Don't need an op amp for that, a dual FET makes a good buffer. Input to gate1, source1 =3D drain2=3D output, source2=3Dgate2=3D-18V and of course drain1 =3D +18V.

Got any 2N5565 in the junk box?

TL081ACP at

Must be FET? How about the TLE2141?

Michael

Yep, but you have to limit signal by 5 volts total.

Date: Tue, Sep 8, 2009, 9:34pm (PDT+7) From: snipped-for-privacy@example.net (Rich=A0Grise) On Mon, 07 Sep 2009 02:45:51 -0700, Bearplug Bearplug Bearplug wrote: Message-ID:

I'm the last surviving Webtv subscriber, now residing in the Cincinnati Zoo. My daily diet is pureed bananas, sunflower seeds, and the occasional human finger.

Soon the curtain will fall on my brief role as an evolutionary step.

I flung doo, but dreamt of flying.

We're on the same page looking at discrete solutions. I avoided them when a single set of supply rails ran everything direct, and an opamp gave the requisite supply rejection. Now there are onboard regulators (on six cards in a row), and an open loop buffer can have isolation.

Your buffer is usually seen with same-size resistors under each source. Otherwise the bottom fet runs at Idss, which is unpredictable and has a large tempco. The output can be zeroed by placing it under the source1 resistor, and adjusting source2 resistor.

Got some 2N3958, but don't need the matching.

If you don't care about the offset, a couple of BF862s (the bottom one with a source resistor) would be the bee's knees. Bypass the daylights out of the resistor or its noise will dominate the noise of the stage.

Cheers

Phil Hobbs

Belay that..20V VDS max. You'd have to cascode them to get to a 34V swing or whatever you're looking at. Of course at audio speeds you could use a 2N7002 instead, with some BJT current source as a source load.

Cheers

Phil Hobbs

Liar. There are several bitter curmudgeons still using Web TV on the antique radio newsgroup. One posts all upper case and sends hate mail if you disagree with him.