Question about the triangular/square wave VCO schematic from the LM13700 datasheet

Frederik De Greef

Other Parts Discussed in Thread: LM13700

Hello,

I used the LM13700 to construct the triangular/square-wave oscillator schematic from the datasheet, it works perfectly.

My interpretation is that the first amp is working as a constant current source, providing a charging and discharging current. But i do not fully understand the use of the 2 push-pull stages, could you please clarify this for me ?

Thank you in advance,

Frederik De Greef

over 11 years ago

0 Michael Stout over 11 years ago

TI__Genius 16890 points

Hello,

Yes, the first amplifier acts as a current source to charge and discharge the capacitor. The Darlington transistors are used as a buffer to make the high impedance output of the first stage into a low impedance for the second stage.

Please see this article that has a lot of information:

http://www.nutsvolts.com/uploads/magazine_downloads/11/May%202003%20Ray%20Marston%20-%20Understanding%20And%20Using%20OTA%20OP-Amps.pdf

Mike

0 Frederik De Greef over 11 years ago in reply to Michael Stout

Prodigy 20 points

Thanks allot for your information Mike!

0 msf over 11 years ago in reply to Frederik De Greef

Prodigy 45 points

The LM13700 seems an old part mainly due to its high voltage requirement and low GBW. How to translate the triangle generator in slau508 to VCO?

Thanks

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Question about the triangular/square wave VCO schematic from the LM13700 datasheet