Gyrator Question

[Wavebourn]

Originally posted by Michael Koster
I'd call that a voltage regulator ;-)

No, it's a PS anti-filter. Or ripple generator.

[ErikdeBest]

Originally posted by revintage
This is how I would implement a Gyrator. Output voltage is set by adjusting R3. Note, devices and component values are random choice.

Hi Lars

The first time I saw something like that was from Broskie...and I liked the idea (simple, good for me )... later on I found Jackinnj's work with the LR8N3

A very interesting feature of the LR8N3 is that it is said to be happy with a meager 0,5mA being drawn through it. I got some LR8N3 and some 400k/2W potentiometers with the intention of building regulated supplies for experiments. I would use a upper resistor of about 1k2 (to set current to 1mA) and the 400k to set the voltage, with maybe a smaller potentiometer in series to allow 'fine adjustments'...but I haven't got that far, yet...

Erik

[revintage]

No, it's a PS anti-filter. Or ripple generator.

Wavebourn, think again, youre so wrong.

[Wavebourn]

Originally posted by revintage


Wavebourn, think again, youre so wrong.

Try the right leg of C1 to the ground and compare. You may add a Zener instead of how C1 is drawn now, to protect the gate against breakdown. Also, it will limit output current on a safe level defined by the resistor R1 value and Zener's breakdown voltage minus Vgs on that current (Ohm's law).

Edit: with 10 Ohm resistor and 12V Zener it will be something about 900 MA.

[Hearinspace]

Originally posted by Michael Koster
I'm trying to understand the purpose of R1 and C1 providing a high AC impedance when that circuit node has a 100uF cap to AC ground.What happens if R1 and C1 (and C3 for that matter) are removed?

I think if this were on a PCB and had 2 or 3 different connections toR1, it could be built as a screen regulator, a high impedance fixed voltage anode load, mu-follower, anti-triode, etc. It's a nice set of functions to have in one place..

On a related note, I'm looking at a DC filament gyrator as an alternative to filament chokes or VCCS. The circuit looks similar to yours but without C3. It would provide fixed voltage (on a controlled ramp) and present a (relatively) high AC impedance to the signal current on the filament.

Cheers, Michael

Originally posted by Wavebourn
Try the right leg of C1 to the ground and compare. You may add a Zener instead of how C1 is drawn now, to protect the gate against breakdown. Also, it will limit output current on a safe level defined by the resistor R1 value and Zener's breakdown voltage minus Vgs on that current (Ohm's law).

Edit: with 10 Ohm resistor and 12V Zener it will be something about 900 MA.

Michael, Wavebourn, could I ask you to post sketches of what you're talking about? A beginner at solid state circuitry, I'm trying to learn from you and am not sure if what I imagine from reading your words is even remotely similar to what you're talking about.

Also Michael, talking about Gyrators on filaments, did you see Rod Coleman's post? If you haven't already you might find it interesting. I built it in simple form (ie. much simpler rectifier and filter front end) and it works well/sounds good. Also tried a version with the top half of his circuit mirrored in the bottom, the whole thing fed by a current source.
Thanks

[Wavebourn]

Hearinspace;
I was talking about Revintage's power supply. As drawn, it is powered from a voltage source with I assume some ripples that he tries to remove like a choke does. Unfortunately, a gyrator is not a choke, and it does not accumulate an energy, so I suggested him to turn it into a source follower that would be more effective in this particular application.

[Hearinspace]

Originally posted by Wavebourn
I was talking about . . .

Thanks, I'll look at that. BTW. I'm just about to sit down to try a couple of MJE5731A's in your High AC Impedance Load ('gyrator') circuit (The one you posted on the Anti-triode thread). Will post if I get it to do any tricks.
Thanks again for your help

[Wavebourn]

Originally posted by Hearinspace



Thanks, I'll look at that. BTW. I'm just about to sit down to try a couple of MJE5731A's in your High AC Impedance Load ('gyrator') circuit (The one you posted on the Anti-triode thread). Will post if I get it to do any tricks.
Thanks again for your help

First of all, let's start from it's task. Whit kind of tube are you going to load? What voltage do you want on a plate? What B+ is in your possession? How big current do you need?

[Hearinspace]

I was just going to try something/anything with a bench power supply. Dig up a tube that fits an already wired socket lying around the bench and start with that. However, If you are willing to lead me through the design process with something (which would be really awesome) then I'll choose something specific. How about a 417A. - Vpk = 150VDC /Ip = 18mA (Vg=-1.5VDC) I'll have up to ~500+VDC available for B+ (the output tube is a 10Y)
Thanks

[Wavebourn]

Originally posted by Hearinspace
I was just going to try something/anything with a bench power supply. Dig up a tube that fits an already wired socket lying around the bench and start with that. However, If you are willing to lead me through the design process with something (which would be really awesome) then I'll choose something specific. How about a 417A. - Vpk = 150VDC /Ip = 18mA (Vg=-1.5VDC) I'll have up to ~500+VDC available for B+ (the output tube is a 10Y)
Thanks

Hmmm... For 350V/18MA it will be 20W dissipation on gyrator transistors.
Do you have also a 350V source? In such case gyrator will have to dissipate less than 4W.