CD4007 what’s ifs

Help Support GroupDIY:

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
Hi all, I hope you’re well…

I was messin around in the old electronics supply store and somehow on the massive wall of ICs a humble CD4007 caught my eye. I looked it up online and saw that it’s a little bundle of complimentary MOSFETs. For some pocket change I bought a few to play with. Why not.

looking online, I see a lot of talk of these being used as CMOS inverters, which I’m still unclear on, despite my research.

I found some other folks that turned it into a guitar pedal, but I think it was really just a class AB amp in a small enclosure…not sure.

Anyway , I’m wondering what you folks could make of this! Any use inside an audio circuit?

Could we do anything creative with it?

I know that P or N channel MOSFETs can be used as clipping diodes by shorting the gate and drain (picture attached). Is it possible to turn this thing into a pack of clipping diodes then?

Poking around with the diode setting on my dmm gives some interesting results…that my inexperience cannot explain.

Could it be pressed into service as a beafy input and output buffer?

Just a thought experiment…And a bit of fun!

Cheers!
 

Attachments

  • 280CB1B1-9A7A-463B-B0A5-900639FECC54.png
    280CB1B1-9A7A-463B-B0A5-900639FECC54.png
    395.7 KB · Views: 53
  • 131AA805-3D60-408E-A3C4-92D216041B09.gif
    131AA805-3D60-408E-A3C4-92D216041B09.gif
    757 bytes · Views: 48

JohnRoberts

Well-known member
Staff member
Moderator
Joined
Nov 30, 2006
Messages
20,594
Location
Hickory, MS
Back in the day the CD4007 was handy... Being able to mix and match the CMOS devices to make oscillators or whatever. You could even trick the simple inverter pair to look like an inverting amplifier. Of course when you try to trick the inverter to act like a linear amp you need to be careful about using too much rail voltage, because both pull up and pull down turned on at the same time can exceed package dissipation. For modest rail voltages it works OK.

JR
 

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
Back in the day the CD4007 was handy... Being able to mix and match the CMOS devices to make oscillators or whatever. You could even trick the simple inverter pair to look like an inverting amplifier. Of course when you try to trick the inverter to act like a linear amp you need to be careful about using too much rail voltage, because both pull up and pull down turned on at the same time can exceed package dissipation. For modest rail voltages it works OK.

JR
Interesting!

Thanks JR.

An oscillator would be kinda cool! Is it possible to get more than just a square wave out if it? I know the clever use of some capacitors and resistors could round the corners a bit, but I'm wondering if we could somehow make a functioning sine wave LFO...

Cheers
 

JohnRoberts

Well-known member
Staff member
Moderator
Joined
Nov 30, 2006
Messages
20,594
Location
Hickory, MS
It's relatively easy to make a square wave oscillator, sine wave not so easy, clean sine wave, don't bother.

One could attempt to use an inverter pair as a gain stage it would have poor open loop gain and rather uncertain DC performance compared to even a cheap op amp.

For voltage or current controlled LFO perhaps check out OTAs (operational transconductance amps).

JR
 

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
It's relatively easy to make a square wave oscillator, sine wave not so easy, clean sine wave, don't bother.

One could attempt to use an inverter pair as a gain stage it would have poor open loop gain and rather uncertain DC performance compared to even a cheap op amp.

For voltage or current controlled LFO perhaps check out OTAs (operational transconductance amps).

JR
Thanks JR,

OTAs are definitely on my list. I was working my way through filters and gyrators before the CD4007 set me down a different path.


Cheers
 

JohnRoberts

Well-known member
Staff member
Moderator
Joined
Nov 30, 2006
Messages
20,594
Location
Hickory, MS
Messing with the CD4007 is close to designing with discrete mosfets. I am a little surprised they still sell them.

JR
 

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
It's an old store haha, but they do seem to be active parts on Mouser...

I'm trying to think of it as a set of discrete MOSFETs, but the pinout is doing my head in. It looks so basic at first, but in practice I can't seem to get it straight.

It'll take some fiddling.
 

rackmonkey

Well-known member
Joined
Sep 20, 2016
Messages
909
Location
Texas
I’ve used the 4007 for the bypass circuit in pedals. Lower parts count as you can do the flip flop and actual switching with one IC.
 

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
I’ve used the 4007 for the bypass circuit in pedals. Lower parts count as you can do the flip flop and actual switching with one IC.
Hey that's a great idea!
Thanks for posting.

Do you happen to have anything drawn up for that?

Cheers
 

JohnRoberts

Well-known member
Staff member
Moderator
Joined
Nov 30, 2006
Messages
20,594
Location
Hickory, MS
I’ve used the 4007 for the bypass circuit in pedals. Lower parts count as you can do the flip flop and actual switching with one IC.
Another benefit is that the MOS transistors on the same substrate will track and behave similarly.

I repeat the caution I already mentioned, when attempting to trick CMOS pairs into linear operation, too much rail voltage can easily exceed device dissipation from parts pulling up and down at the same time.

JR
 

MisterCMRR

Well-known member
Joined
Jul 1, 2019
Messages
93
Location
Ventura, CA
As I remember, the open-loop gain of each inverter is about 10x and you can run them easily in self-bias to make a high-gain AC amplifier (I've used this at the front end of a phase-locked-loop, for example). Just connect the opposing drains in stages 1 and 2 the same way they're internally connected in stage 3. Then put a 10 MΩ resistor from input to output of each inverter stage (this makes in and out sit half-way between rail voltages. Then AC couple input signal to stage 1, AC couple stage 1 to stage 2, etc. So overall gain is now about 10 x 10 x 10 = 1000 ... and will do rather soft limiting. They're very handy little parts.

And you can do all sorts of amazing tricks with OTA (transconductance amplifiers). I've done intentional slew-rate limiting, which can be changed by varying the bias current). And just putting a capacitor as load on the output and using with a pair of comparators, you can build a perfect triangle-wave generator and vary the frequency with bias current. And lots more ...
 

AVA

Well-known member
Joined
Jun 7, 2021
Messages
47
Location
Canada
Wow! There is so much to unpack here

OTA's are another thing that I'm slightly obsessing over right now. I just ordered some LM13700 and NE5517's. We'll see what happens. I read in some dark corner of the internet that OTA's are slowly dying? Is there a chance that they'll be non existent in the near future? That would be foolish, no?

I'm going to try and put together this high gain AC amp using the 4007. I'll probably read that post 900 times in doing so haha. It's my attempt at finishing one thing before starting another.

Cheers guys! Thanks for your time
 

JohnRoberts

Well-known member
Staff member
Moderator
Joined
Nov 30, 2006
Messages
20,594
Location
Hickory, MS
4007s make low gain AC amps...
==
I used lots of OTAs last century... these days it is cheaper and easier to do it digital. But IMO it is worthwhile to understand analog first.

JR
 

gyraf

Well-known member
Staff member
Moderator
Joined
Jun 4, 2004
Messages
10,217
Location
Aarhus, Denmark
- and as bypass "relay" in e.g .the TC 1140 equalizer:
 

Attachments

  • TC1140_schematic_all.gif
    TC1140_schematic_all.gif
    115.8 KB · Views: 21
Top