Re: Differential Amplifier Plugin Questions


Yes, I've seen at least one video where one of the gears was broken. I saw another picture where it appears someone had cut a new gear from nylon/delrin. I do think I like the digital model better.

Barry - N4BUQ

----- Original Message -----
From: "zentronics42" <>
To: "tekscopes" <>
Sent: Sunday, January 23, 2022 11:27:25 AM
Subject: Re: [TekScopes] Differential Amplifier Plugin Questions
On The 7A13 bias to the digital model if possible. The plastic gearing in the
analog ones are starting to age out and crack. This is not an easy assembly to


-----Original Message-----
From: <> On Behalf Of John Kolb
Sent: Sunday, January 23, 2022 1:41 AM
Subject: Re: [TekScopes] Differential Amplifier Plugin Questions

the 7A22 does have an internal adjustable offset voltage, it's just not
calibrated or presented on a mechanical display. it's turned on by setting the
LF -3dB POINT switch to the DC position connected to the OFFSET adjust knobs
with the gray line.

The 7A13 has a 100 MHz BW and is useful when a calibrated offset voltage is
useful. We used them at Wavetek to set the triangle peaks to exactly
+ and - 2.5V.

The 7A22 is useful when you need sensitivity up to 10 uV/Div, need
adjustable LF and HF filtering and can live with a 1 MHz maximum bandwidth.


On 1/22/2022 9:27 AM, n4buq wrote:
While troubleshooting various aspects of my scopes, I've encountered waveforms
in the manuals where a very small signal is displayed at/near the center of the
displayed image with a + or - value shown to the side of the display and I'm
just now realizing that those images were made while using a differential
amplifier and I'm considering obtaining one. I can typically see the waveforms
by switching to AC input mode but that may not be quite as good as using a
differential measurement method.

I see where the "popular" versions for the 7000 series is either a 7A13 or 7A22.
The 7A13 (either the mechanical or digital model) seem to be perhaps the
easiest to use due to the offset/comparison voltage is provided internal to the

For the 7A22, is it still just a case of providing an external offset voltage in
one input and the signal to be measured is applied to the other input? That
seems logical but thought I'd ask for some general guidelines before getting
one of them.

Barry - N4BUQ

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