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Yes, and I posted that I understood the error.

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On Sun, May 11, 2025 at 10:21 AM, John Woodgate wrote:

I have uploaded the above as a .ZIP. According to Bob Pease, the gain at the peak should be close to 34 dB, independent of the tuned frequency. I don't get either of those results using version 24.1.8. ...

Have you corrected the position of the OUT node?

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Thank you very much.

for instance.

Being lazy, I searched for "another single pot tunable band pass network called Hall’s network"

DaveD
KC0WJN

On Mon, May 12, 2025 at 04:41 John Woodgate via <jmw=[email protected]> wrote:

Thank you:Do you have a reference to it? Google doesn't help, because the name has been re-used. The Pease circuit will tune over a decade with 100:1 change in R2 value, which is just about practicable, 100 ohms/100k.

On 2025-05-12 00:21, Jeff Furman via wrote:

There is another single pot tunable band pass network called Hall’s network.

it can tune over a decade. The commercial worked example is used in the general radio model 1232a tuned amplifier/null detector. It is a different circuit than Pease’s.

Jeff Furman AD6MX

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I haven't seen Pease's original diagram. I was going strictly by the EDN article.

This is a recent article, and I know from experience that the EDN editors encourage writers to supply their own diagrams, at least for their "Design Ideas". Perhaps main articles are different. But given the error in the article name, anything's possible.

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Thank you:Do you have a reference to it? Google doesn't help, because the name has been re-used. The Pease circuit will tune over a decade with 100:1 change in R2 value, which is just about practicable, 100 ohms/100k.

There is another single pot tunable band pass network called Hall’s network.

it can tune over a decade. The commercial worked example is used in the general radio model 1232a tuned amplifier/null detector. It is a different circuit than Pease’s.

Jeff Furman AD6MX

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Figure 1 was probably drawn by an EDN person. Bob's rough sketch is OK. I was taking the output from the wrong place.

You should also note, John, that there are errors in the EDN article.

The first picture shows the opamp in non-inverting configuration - this is, of course positive feedback, and sure enough it will latch to one of the rails.

Further down in the article, variations of the circuit are re-drawn in the inverting configuration - this is the correct version.

It is a quirk of AC analyses that sometimes an unstable configuration appears to be stable, when in fact it isn't. Always check in the time domain!

I presume Bob got it right. He would never have made that mistake. I'm surprised nobody else pointed that out.

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Tony

On 11/05/2025 16:20, John Woodgate via groups.io wrote:

I have uploaded the above as a .ZIP. According to Bob Pease, the gain at the peak should be close to 34 dB, independent of the tuned frequency. I don't get either of those results using version 24.1.8. However, the bandwidth is fairly constant with frequency, as predicted. I can't believe Bob Pease reported the performance in error.

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You should also note, John, that there are errors in the EDN article.

The first picture shows the opamp in non-inverting configuration - this is, of course positive feedback, and sure enough it will latch to one of the rails.

Further down in the article, variations of the circuit are re-drawn in the inverting configuration - this is the correct version.

It is a quirk of AC analyses that sometimes an unstable configuration appears to be stable, when in fact it isn't. Always check in the time domain!

I presume Bob got it right. He would never have made that mistake. I'm surprised nobody else pointed that out.