Slew rate control circuit

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Wenye

Joined: 21 May 2003
Posts: 32
Helped: 1

22 Jan 2004 17:13 bjt slew rate control

Hi All,

Does anyone has idea in adjustable slew rate circuit.
I need a circuit that can adjust slew rate of rising and falling edge separately. And the adjustable rate from 1ns to 100ns in 0.5 or 1ns per step.

Does anyone has idea in this?

Thank you in advance!

Wenye

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22 Jan 2004 17:13 Ads

electronrancher

Joined: 24 Mar 2002
Posts: 505
Helped: 34

27 Jan 2004 7:32 slew rate control circuit

use a current.

adjustable should be easy, use a V/I converter. input an adjustable voltage to an opamp + terminal and output to base of bjt or gate of mosfet. now at the bottom (emitter) of bjt, you put a 1k for 1mA/V (or 10k for 100uA/V or 100k for 10uA/V or...) Last, connect the - input of the opamp to top of resistor.

Now, if you put 1v as the input, the op amp will increase base drive until there is 1mA flowing through the bjt and into the 1k, to make voltage at - terminal equal to voltage at + terminal, 1v. The collector is the current sink. Change input voltage to 2v, this guy will sink 2ma into the collector

It's called op amp V/I converter - look it up on google..