Dual MOSFET in a package.

For use a in long tail VCA experiment i came along these two.

IRF7303
V DSS = 30V
R DS(on) = 0.050Ω

IRF7314
V DSS = -20V
R DS(on) = 0.058Ω

Would one rate them as suitable?
their part number is fairly close and might look like complementary.

Suitable for what? or rather, in what aspect?

Analog_Fan said:

For use a in long tail VCA experiment i came along these two.

IRF7303
V DSS = 30V
R DS(on) = 0.050Ω

IRF7314
V DSS = -20V
R DS(on) = 0.058Ω

Would one rate them as suitable?
their part number is fairly close and might look like complementary.

Click to expand...

Huh? MOSFET in VCA? That would be a first.
Now, a long tail with different polarities?
Can you post a schemo?

VCAs generally use bipolar transistors inside.

JR

JohnRoberts said:

VCAs generally use bipolar transistors inside.

JR

Click to expand...

Well about a year ago, i discovered this site: sound-au.com.
it has some articles on VCA's, that's where the idea came from, just wanna give a try and compare vs my CA3080, LM13700 vca's.
the Falstad simulator shows it should work, i don't have a spectrum analyzer.

On a Hackaday YouTube video witch had the subject to reverse engineer the die of a chip.
that guy said today they use FET's instead of bipolar transistor, but JFET don't seem to cut the mostard according the simulator

Die images:
https://zeptobars.com › en
CD4000 contains 2x 3-input NOR gate + 1x inverter gate. Die size 1722x1394 µm. Datecode 749. Infineon BFP450 - highly linear low noise BJT, 24Ghz fT : weekend die-shot I like that it is complex for a BJT, yet one can see everything without de-layering. You can compare it to BC858C (fT 250 MHz), BFP540 (fT 30 GHz) and BFR740 (fT 42 GHz).

abbey road d enfer said:

Huh? MOSFET in VCA? That would be a first.
Now, a long tail with different polarities?
Can you post a schemo?

Click to expand...

just a normal Long Tail vca found on sound-au.com with a differential opamp.
that page has some using fet's,but fet's don't seam to cut the mostard.

Analog_Fan said:

just a normal Long Tail vca found on sound-au.com with a differential opamp.
that page has some using fet's,but fet's don't seam to cut the mostard.

Click to expand...

Just posting the website is of no help, please link a specific schematic.

Analog_Fan said:

just a normal Long Tail vca found on sound-au.com with a differential opamp.

Click to expand...

I know the website, but there's hundreds of pages there. What project is it?

Analog_Fan said:

just wanna give a try and compare vs my CA3080, LM13700 vca's.

Click to expand...

Both are very mediocre VCA's.

Analog_Fan said:

On a Hackaday YouTube video witch had the subject to reverse engineer the die of a chip.
that guy said today they use FET's instead of bipolar transistor, but JFET don't seem to cut the mostard according the simulator

Click to expand...

So who are you going to believe? the guy on YouTube or the simulator? Dilemma...

Analog_Fan said:

Die images:
https://zeptobars.com › en
CD4000 contains 2x 3-input NOR gate + 1x inverter gate. Die size 1722x1394 µm. Datecode 749. Infineon BFP450 - highly linear low noise BJT, 24Ghz fT : weekend die-shot I like that it is complex for a BJT, yet one can see everything without de-layering. You can compare it to BC858C (fT 250 MHz), BFP540 (fT 30 GHz) and BFR740 (fT 42 GHz).

Click to expand...

I don't really see how this is relevant to this discussion.

abbey road d enfer said:

I know the website, but there's hundreds of pages there. What project is it?

Click to expand...

https://sound-au.com/project213.htm
Project 213

accept i added a current mirror instead and used mosfets.

Analog_Fan said:

Well about a year ago, i discovered this site: sound-au.com.
it has some articles on VCA's, that's where the idea came from, just wanna give a try and compare vs my CA3080, LM13700 vca's.

Click to expand...

Technically those are OTAs (operational transconductance amps), VCAs operate using different principles.

The LSK 389 is a JFET not MOSFET.

It might work after a fashion, I am not familiar with the transconductane law of mosfets.

good luck.

JR

Analog_Fan said:

the Falstad simulator shows it should work, i don't have a spectrum analyzer.

On a Hackaday YouTube video witch had the subject to reverse engineer the die of a chip.
that guy said today they use FET's instead of bipolar transistor, but JFET don't seem to cut the mostard according the simulator

Die images:
https://zeptobars.com › en
CD4000 contains 2x 3-input NOR gate + 1x inverter gate. Die size 1722x1394 µm. Datecode 749. Infineon BFP450 - highly linear low noise BJT, 24Ghz fT : weekend die-shot I like that it is complex for a BJT, yet one can see everything without de-layering. You can compare it to BC858C (fT 250 MHz), BFP540 (fT 30 GHz) and BFR740 (fT 42 GHz).

Click to expand...

abbey road d enfer said:

Both are very mediocre VCA's.

Click to expand...

they might be in the pro audio world, but common practice in a synthesizer alongside a transistor long tail.
I got a cool audio 2164 cloned ic, but not yet dedicated time to, don't have a idea of a c.v control circuit yet.

abbey road d enfer said:

So who are you going to believe? the guy on YouTube or the simulator? Dilemma...

Click to expand...

indeed, but i assume the simulator is right.
I get better results from the simulator using mosfet than jfet.

Do you think the parts i have chosen are suitable in a +/-12V synthesizer environment.
they seam to be complementary, like the (BC547 & BC557), (2SA733 & 2SC945 used by Roland).

abbey road d enfer said:

I don't really see how this is relevant to this discussion.

Click to expand...

Just in case you didn't have seen this website, pretty interesting images.

Analog_Fan said:

indeed, but i assume the simulator is right.

Click to expand...

The simulator is as right as its models. Models are the weak links in simulators.

Analog_Fan said:

they seam to be complementary, like the (BC547 & BC557), (2SA733 & 2SC945 used by Roland).

Click to expand...

I don't see complementary devices in your proposed schematic.

abbey road d enfer said:

I don't see complementary devices in your proposed schematic.

Click to expand...

i meant the mosfet datasheets from witch i started the topic.
Just to build a "old skool" vca module, but a bit more modern than old/early Moog devices, touch implying silica product but not ic's.
they are rated for 20/30 Volts. the signal inside is 10 V.p.p.

the search engine from mouser doesn't seem to do what you want (sometimes) if you wanna filter or try too.
Yesterday i tried again for onsemi, toshiba products (dual mosfets), though the voltage range was in range, their datasheet said things like: digital logic, battery control, motor control and if you find a N channel it quite a challenge to find the counter P channel part, like a day job.

Analog_Fan said:

i meant the mosfet datasheets from witch i started the topic.
Just to build a "old skool" vca module, but a bit more modern than old/early Moog devices, touch implying silica product but not ic's.
they are rated for 20/30 Volts. the signal inside is 10 V.p.p.

the search engine from mouser doesn't seem to do what you want (sometimes) if you wanna filter or try too.
Yesterday i tried again for onsemi, toshiba products (dual mosfets), though the voltage range was in range, their datasheet said things like: digital logic, battery control, motor control and if you find a N channel it quite a challenge to find the counter P channel part, like a day job.

Click to expand...

You're becoming more and more obscure.
Why do you need complementary MOSFET's?

If you are about to experiment with a 2164 you might want to look at the last post in this thread.
https://groupdiy.com/threads/coolaudio-ics.64110/page-2#post-972457

abbey road d enfer said:

You're becoming more and more obscure.

Click to expand...

not my intention tough, not native ...

abbey road d enfer said:

Why do you need complementary MOSFET's?

Click to expand...

well, I'm used to "work" with common used transistor pairs, like 2SA733 and 2SC945.
i see them as man and wife
they have a pretty similar hFe and characteristics.

VCAs for pro audio is a 'solved problem' with some great solutions from THAT. VCAs for synths are more in the category of guitar amps, you don't perfect, you want interesting. I say build some circuits, see if they match your simulation, send some audio through and see if you like the results. Best case you've come up with a new topology that gives your synth some distinct character, worst case you go back to the usual culprits and you've learned a lot.

Rob Flinn said:

If you are about to experiment with a 2164 you might want to look at the last post in this thread.
https://groupdiy.com/threads/coolaudio-ics.64110/page-2#post-972457

Click to expand...

well, Uli Behringer is known for copy and paste.
They even "robbed" Ba662A clone based on matched pair transistors from OpenMusicLabs and used it in their TD3, before they made their own silicon version of the BA662. i believe they have a lab in Hong Kong.

NOON said:

VCAs for pro audio is a 'solved problem' with some great solutions from THAT. VCAs for synths are more in the category of guitar amps, you don't perfect, you want interesting. I say build some circuits, see if they match your simulation, send some audio through and see if you like the results. Best case you've come up with a new topology that gives your synth some distinct character, worst case you go back to the usual culprits and you've learned a lot.

Click to expand...

that's exactly what i wanna do, a not so perfect VCA made from individual parts rather than ic's.
But i do design pcb's from the get go, hate breadboard, made a few months ago, the parts i have chosen are SOIC8 instead of SOT3..., a bit easier to solder for me, haven't soldered silicon SMD parts yet.

Just wanted an opinion from people on these parts.
IRF7303
IRF7314

the Datasheets of FETs, transistors are somewhat more "dificult" than for example a CD4053, CD4030, CD4021.