Hello,
for an amplifier projekt I'm looking for a constant current source
10-30mA but -3000V. A series of 1000 V MOSFETs for example? Any suggestions?
Best regards
oliver
for an amplifier projekt I'm looking for a constant current source
10-30mA but -3000V. A series of 1000 V MOSFETs for example? Any suggestions?
Best regards
oliver
Maybe you should tell what voltage variations you expect on
the 3kV, since it might matter for the choice of solution. It is
quite a difference if you expect max 100V or max 1kV variation.
the 3kV, since it might matter for the choice of solution. It is
quite a difference if you expect max 100V or max 1kV variation.
Need to know the input voltage range and also the load voltage and whether or not the load can become shorted.
Excuse me that I did not tell more details before. I have build this amplifier to drive electrostatic loudspeakers. In the final stage, two tetrodes (4x150a) with anode resistor (120k, 40W) work as well known anode amplifier, push pull to drive the two stators of the electrostatic loudspeaker. Voltage supply ist +3000V, anode quiescant voltage +1500, swing ist +500 to +2500, for example.
The problem ist, that resistors of this kind in good quality are very expensive and my one is composed of 40 metal film resistors...
It is already working, but now I like to do some improvements.
So I thought, why not try a constant current source instead of the resistors?
Many thanks for your interest in my "ideas"
Best regards
oliver
The problem ist, that resistors of this kind in good quality are very expensive and my one is composed of 40 metal film resistors...
It is already working, but now I like to do some improvements.
So I thought, why not try a constant current source instead of the resistors?
Many thanks for your interest in my "ideas"
Best regards
oliver
from first hand experience (ham radio stuff and photomultipliers) I can tell you that very peculiar stuff starts to happen when you go over about 700 volts -- things like humidity, presence of dirt, proximity, non-linearity of resistors etc.
You probably want to rethink using standard PCB materials, insulations etc. You can also wire bipolar devices in series -- there's an example in "the art of electronics".
BTW, Kepco sells replacement MOSFET devices for their very high voltage supplies -- used by the folks at Oak Ridge and Lawrence Livermore Labs, places like that --
You probably want to rethink using standard PCB materials, insulations etc. You can also wire bipolar devices in series -- there's an example in "the art of electronics".
BTW, Kepco sells replacement MOSFET devices for their very high voltage supplies -- used by the folks at Oak Ridge and Lawrence Livermore Labs, places like that --
Two words:
Tubes
Cascode
You can cascode current sources, and tubes make fine current sources. Stack two (or more) tubes on top of one another in a cascode and you can deal with truly prodigious voltages.
Real world example? The front end in the Atmasphere amps. They use cascoded 6SN7s as the current source for the differential. Granted, the voltage is a lot lower, but the concept is what you're after.
Grey
Tubes
Cascode
You can cascode current sources, and tubes make fine current sources. Stack two (or more) tubes on top of one another in a cascode and you can deal with truly prodigious voltages.
Real world example? The front end in the Atmasphere amps. They use cascoded 6SN7s as the current source for the differential. Granted, the voltage is a lot lower, but the concept is what you're after.
Grey
More voltage Igor !
Perhaps something simpler like a centre-tapped choke ? Surely this would relax the death-volts requirement and make the power supply simpler and , errr , cheaper !
316a
Perhaps something simpler like a centre-tapped choke ? Surely this would relax the death-volts requirement and make the power supply simpler and , errr , cheaper !
316a
Re: 4CX150
Yes, provided that you feed the upper x150 with its own heater transformer (which should have a really good primary to secondary insulation). Center tap this and connect to the cathode.
I'm just thinking out loud 🙂
316a said:
Yes, provided that you feed the upper x150 with its own heater transformer (which should have a really good primary to secondary insulation). Center tap this and connect to the cathode.
I'm just thinking out loud 🙂
Re: Re: 4CX150
Unlikely , once the lower 4CX150 swings +/- 500 volts , this will certainly stretch the h-k ratings even if the top valve has floated heaters on a seperate transformer winding . I've already considered SRPP for my ESL treble panels which don't need large voltage swings , series regulator valves such as the 12E1 and 6080 have h-k limits of 300V which would work but doubtful that tx valves are intended to have ratings this high . With a panel requiring several thousand volts P-P , SRPP or CCS loading is wasteful of already dangerous HT , making the power supply an extreme health (and wealth!) hazard , therefore I recommend choke loads for ESL panels instead of the current resistive load elements . Lower HT can then be used and it's less wasteful in terms of heat
316a
Jax said:
Unlikely , once the lower 4CX150 swings +/- 500 volts , this will certainly stretch the h-k ratings even if the top valve has floated heaters on a seperate transformer winding . I've already considered SRPP for my ESL treble panels which don't need large voltage swings , series regulator valves such as the 12E1 and 6080 have h-k limits of 300V which would work but doubtful that tx valves are intended to have ratings this high . With a panel requiring several thousand volts P-P , SRPP or CCS loading is wasteful of already dangerous HT , making the power supply an extreme health (and wealth!) hazard , therefore I recommend choke loads for ESL panels instead of the current resistive load elements . Lower HT can then be used and it's less wasteful in terms of heat
316a
Re: More voltage Igor !
This is exactly the path that I've taken with my d-d ESL amp. The downside is that you have to think about level shifting if you don't have well-insulated stators.
316a said:
This is exactly the path that I've taken with my d-d ESL amp. The downside is that you have to think about level shifting if you don't have well-insulated stators.
That's why I suggested connecting the heater supply to the cathode so it follows the signal voltage 🙂
Anyhow, it was just me thinking, I would not build this myself. Circuits with >1kV requires experiences beyond normal.
Anyhow, it was just me thinking, I would not build this myself. Circuits with >1kV requires experiences beyond normal.
Jax said:
Absolutely! This sort of circuit can be FATAL if you don't know exactly what you're doing.
Leakage
With the heater connected to the cathode , the transformer leakage capacitance needs to be driven 🙁
I'm also a 1KV virgin , even 700V scares the crap out of me . Mind you I've been lit up by the 1400V diaphragm supply a few times , not too bad , like a static shock but it brings home the dangers of what a large capacitance high current EHT supply can do
316a
Jax said:
With the heater connected to the cathode , the transformer leakage capacitance needs to be driven 🙁
I'm also a 1KV virgin , even 700V scares the crap out of me . Mind you I've been lit up by the 1400V diaphragm supply a few times , not too bad , like a static shock but it brings home the dangers of what a large capacitance high current EHT supply can do
316a
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