Transistor Vbe Matching Using A Commutating Chopper-Based Circuit

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mediatechnology
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Re: Transistor Vbe Matching Using A Commutating Chopper-Based Circuit

Post by mediatechnology » Wed Oct 07, 2020 2:01 pm

I finally got the Vbe Matcher off of a Protoboard by moving it to Vectorboard.

It's been awhile since I did point-to-point Vectorboard.

The connections across the top are Power, 'Scope Monitor Out (filtered), Output to A/D, 1.5 mV P-P Calibration signal, 15V Trigger output.

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The two jumpers and shunts switch the test socket from NPN to PNP.

There are two rows in the test socket.
The right-hand row is for CBE pinout transistors.
The left-hand row is for BCE pinouts.

Image

The clip is to thermally equalize the test transistors.

A pair of BD139 BCE pinout transistors:

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A 2SB737 pair:

Image

One more project I can check off the list...
It's been a productive few weeks.
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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mediatechnology
Posts: 4550
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
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Re: Transistor Vbe Matching Using A Commutating Chopper-Based Circuit

Post by mediatechnology » Thu Oct 08, 2020 12:54 pm

JR. wrote:
Sun Dec 22, 2019 9:38 am
If you add a 50k or so resistor from the junction of the two emitters to ground that would prevent potential reversed junctions from zenering when switched for the wrong polarity.

JR
I added D1-D4 to clamp Ve.
Not only for the reason JR gives but also to reduce recovery time for when both devices are removed from the test socket.
Without D1-D4 Ve goes to the rail when Q1 and Q2 are removed.

Image
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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