I am working on a high voltage opamp for the pre-amp to a MOSFET voltage follower. What do you guys think about this schematic?
I am planning on using SOT-223 ZETEX HIGH Voltage Devices for the diff amp stage and there High current devices in the output stage.
I want this thing to operate at +/-100v and drive a mosfet power follower. Caps are TBD values. I dont have a good spice program yet to simulate.
I am planning on using SOT-223 ZETEX HIGH Voltage Devices for the diff amp stage and there High current devices in the output stage.
I want this thing to operate at +/-100v and drive a mosfet power follower. Caps are TBD values. I dont have a good spice program yet to simulate.
Attachments
Your currentmirror Q1 and Q2 need a connection from their base to Q1 collector.
Place a bias resistor over C9.
Try find BJT with a high "va" and run them at ~.5 - 1 mA.
FZX493 and FZX593 is a good device from Zetex.
The spice data says :
NF = .99
Va = 270
Sonny
Place a bias resistor over C9.
Try find BJT with a high "va" and run them at ~.5 - 1 mA.
FZX493 and FZX593 is a good device from Zetex.
The spice data says :
NF = .99
Va = 270
Sonny
Now i have a little more time.
You do know that C1 does not have a function?.
Why do you have installed C2,C3,C4,C6,C7??? They are not necessary. C5 (compensation cap) is enough to control the opamp's freq. response/phase margin.
Sonny
You do know that C1 does not have a function?.
Why do you have installed C2,C3,C4,C6,C7??? They are not necessary. C5 (compensation cap) is enough to control the opamp's freq. response/phase margin.
Sonny
Preamp
The 4 output Transistors will blow, the current mirror Q1,Q2 will need biasing.
Regards:
Arne
The 4 output Transistors will blow, the current mirror Q1,Q2 will need biasing.
Regards:
Arne
OOPS. I sent the old schematic. The base connection of the current mirrors should be there. I wanted to put spaces where I could put capacitors or other components to play with the circuit.
I Am not sure what output devices to use yet. I need to find something beefy.Thanks for the input
I Am not sure what output devices to use yet. I need to find something beefy.Thanks for the input
I doubt that you need this much output stage just
to drive the inputs of MOSFET followers. Maybe
you should dump the outputs and just use the drivers.
to drive the inputs of MOSFET followers. Maybe
you should dump the outputs and just use the drivers.
For a free spice version: http://www.winspice.com/
No schematic entry, but fast.
Suggestions:
- 2 small resistors (50-300 Ohm) in series with the emitors of the curent mirror Q1 Q2
- 2 even smaller resistors (10-30 Ohm) in series with the input pairs emitor Q4 Q5
- use leds to bias the current sources, zeners can be very noisy
- take a look at transistors meant for video stages, plenty of gain and voltage.
No schematic entry, but fast.
Suggestions:
- 2 small resistors (50-300 Ohm) in series with the emitors of the curent mirror Q1 Q2
- 2 even smaller resistors (10-30 Ohm) in series with the input pairs emitor Q4 Q5
- use leds to bias the current sources, zeners can be very noisy
- take a look at transistors meant for video stages, plenty of gain and voltage.
- Status
- Not open for further replies.