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Opamp for High Frequency Output - Need Help

Acoipat

Jan 13, 2017
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Jan 13, 2017
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Hi,

I need help designing a circuit that is intended to drive a 30Vpp 10MHz AC output. I am attempting to use a basic non-inverting opamp setup with a closed-loop gain of 6 (can be easily adjusted) to amplify an input from a function generator. With my setup, the gain drops off at frequencies above 10kHz. This is nowhere near the frequency I need. At frequencies > 1MHz, there is no signal being read at all.

As I'm not too familiar with opamps, I'm not sure if I am missing something in the specifications of the opamp, or need to have something specific in my circuit setup? I tried to pick an opamp with a high Gain Bandwith product. Are there any opamps that can be recommended, or if there is a better (simple) way to produce such an output without an opamp?

The opamp I am using is the LT1365CN (link to data sheet).


Thanks for any help.
 

davenn

Moderator
Sep 5, 2009
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Hi
welcome to EP :)

I need help designing a circuit that is intended to drive a 30Vpp 10MHz AC output. I am attempting to use a basic non-inverting opamp setup with a closed-loop gain of 6 (can be easily adjusted) to amplify an input from a function generator. With my setup, the gain drops off at frequencies above 10kHz. This is nowhere near the frequency I need. At frequencies > 1MHz, there is no signal being read at all.

have you got any circuit at all for a possible design ?
component values, lead length on components etc will be VERY critical
this may not work on one of those plug in breadboards due to capacitive and inductive problems at those frequencies

show us a photo of your construction and circuit

Dave
 

duke37

Jan 9, 2011
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You could look up circuits for radio transmitters, these are usually tuned circuits with neutralised transistors. High frequency transistors will be required, fets seem to be the current fashion.

30V is quite lively and a transformer may be the way to go to run from a lower voltage.
 

BobK

Jan 5, 2010
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The datasheet shows ±7.5V with ±15V supplies. It is not capable of 30Vpp

Bob
 

Acoipat

Jan 13, 2017
2
Joined
Jan 13, 2017
Messages
2
Hi
welcome to EP :)



have you got any circuit at all for a possible design ?
component values, lead length on components etc will be VERY critical
this may not work on one of those plug in breadboards due to capacitive and inductive problems at those frequencies

show us a photo of your construction and circuit

Dave
Thanks for the welcome. :)

I was using a circuit setup essentially identical to the one attached, although I was using resistors of higher value, and have been told to use lower resistances(like the values in the attachment). I don't happen to have a photo of the circuit but it's built on a standard breadboard (I know they struggle with high frequencies, but even testing with 1MHz produces no output).
You could look up circuits for radio transmitters, these are usually tuned circuits with neutralised transistors. High frequency transistors will be required, fets seem to be the current fashion.

30V is quite lively and a transformer may be the way to go to run from a lower voltage.
I will look into this, thanks.
The datasheet shows ±7.5V with ±15V supplies. It is not capable of 30Vpp

Bob
Sorry if this is dumb, but could you point out where on the datasheet it specifies this? Thanks
 

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