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Old 29th March 2020, 12:58 PM   #31
Bonsai is offline Bonsai  Europe
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I’ve used the 4051 in industrial applications switching uV through to volt signals with great success - if you follow a few very basic rules they work really well. The most important 2 points are

1. limit the current into the switch and/or ensure the signal voltage does not exceed the supply rails.
2. Keep the digital control signals within the supply rails. If you go to the supply rails or higher, they distort. I found this out the hard way switching uV signals where I got non-linearity issues.

The integrated ESD protection diodes do a good job, but they are ‘leaky’ as they approach forward conduction and cause linearity problems.

Last edited by Bonsai; 29th March 2020 at 01:04 PM.
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Old 29th March 2020, 03:07 PM   #32
MarcelvdG is offline MarcelvdG  Netherlands
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That's interesting... I wouldn't have thought of issue 2.

According to https://assets.nexperia.com/document...t/HEF4051B.pdf , see the attached figure, the bulk of the pass gate NMOS is switched to the Y terminal when a switch is on, presumably to reduce on resistance and on resistance variations. Apparently the HEF4000 ICs are made in a process with N-type substrate, or at least that is my educated guess seeing that all PMOS bulks are hardwired to the supply while NMOS bulks are connected to different nodes.

As a result, you probably get substrate coupling issues whenever any terminal goes enough above the positive supply to cause forward conduction. The ESD diodes to VDD are probably series of N+ and P+ stripes placed straight in substrate. When an input goes too high, its anode, the substrate and the P-type source and drain regions of any PMOS form a giant lateral PNP transistor. The ESD diode anode then acts as the emitter, the substrate as the base and the sources and drains of all PMOS transistors as collectors.
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Old 29th March 2020, 03:25 PM   #33
synonymous is offline synonymous  United States
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If you need help designing a PCB, I can help you.
Draw up a scheme and give me some specs for mounting etc..
You can send the files to JLCPCB and get a handful of boards for cheap.
Careful for the addiction, I just tossed about 65 lbs of unused boards the other day.

S
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Old 30th March 2020, 05:11 AM   #34
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by MarcelvdG View Post
That's interesting... I wouldn't have thought of issue 2.

According to https://assets.nexperia.com/document...t/HEF4051B.pdf , see the attached figure, the bulk of the pass gate NMOS is switched to the Y terminal when a switch is on, presumably to reduce on resistance and on resistance variations. Apparently the HEF4000 ICs are made in a process with N-type substrate, or at least that is my educated guess seeing that all PMOS bulks are hardwired to the supply while NMOS bulks are connected to different nodes.

As a result, you probably get substrate coupling issues whenever any terminal goes enough above the positive supply to cause forward conduction. The ESD diodes to VDD are probably series of N+ and P+ stripes placed straight in substrate. When an input goes too high, its anode, the substrate and the P-type source and drain regions of any PMOS form a giant lateral PNP transistor. The ESD diode anode then acts as the emitter, the substrate as the base and the sources and drains of all PMOS transistors as collectors.
Sorry, I meant to write that the sources and drains of all PMOS transistors and the switched bulk of the pass gate NMOS act as parasitic collector. That switched bulk is probably larger and more effective as a collector than the PMOS drain/source stripes.
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Old 31st March 2020, 01:24 AM   #35
R1234 is offline R1234  Australia
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Thanks MarcelvdG, but I will pass for the moment.

OlegSh, you are quite correct about plug-in PCB's, BUT, - over 40 years ago I simply used a solder coated board & lightly chamfered the edges. They were plugged into Gold Plated sockets with a spray of cleaner lubricant. I have used this scheme ever since with no problems.

We were only doing relatively small runs but had no trouble at all, and, it was wonderful being able to swap boards around instantly for checking, comparing & fault-finding. Some of these original 40 year old Hi-Fi amplifiers are still giving good service to-day & I have one in my hobby room. I have no desire to change, particularly when I have a good stock of parts for making up the sockets with gold-plated pins.

Now, synonymous, thanks very much for your kind offer. - I don't relish PCB layout design and these days I don't have other people to do it for me ! - I do have express PCB, though have not used it yet, but don't know of JLCPCB so am guided by you. Sounds interesting though, as I have lots of ideas (crazy thoughts), about comparing different RIAA schemes to complement my hundreds of good classical LP's.
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Old 31st March 2020, 07:21 AM   #36
mchambin is offline mchambin  France
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Quote:
plug-in PCB's
I used Rhodium plated contacts in 3M connectors.
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