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The '''LM13700''' (co-invented by Bill Gross and Don Sauer)<ref name="mfos">[http://www.musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&PROJARG=ELECTRONICS/acknowledgements.html&CATPARTNO=&PN=1&SONGID=NONE Acknowledgements], Music From Outer Space website</ref> consists of two current controlled [[operational transconductance amplifier]]s (OTA), each having differential inputs and a push-pull output. The LM13700 is like a standard [[op-amp]]: each has a pair of differential inputs and a single output, but an OTA is voltage in and current out rather than voltage in and voltage out; and OTAs are programmable via the I<sub>ABC</sub> pin. Linearizing diodes at the input reduce distortion and allow increased input levels. The darlington output buffers provided are specifically designed to complement the wide dynamic range of the OTA. This chip is very useful in audio electronics especially in [[analog synthesizer]] circuits like [[voltage controlled oscillator]]s, [[voltage controlled filter]]s, and [[voltage controlled amplifier]]s. The darlington output buffers on the LM13700 are different from those on the LM13600 in that their bias currents (and hence their output DC levels) are independent of I<sub>ABC</sub> pin. This usually results in performance superior to that of the LM13600 in audio applications.
== Unused buffers ==
When an external [[operational amplifier|op-amp]] is used instead of the internal darlington buffers the unused buffer pins can safely be left floating.<ref>[https://e2e.ti.com/support/amplifiers/f/14/t/264305?Terminating-unused-darlington-buffer-in-LM13700- Terminating unused darlington buffer in LM13700?], TI E2E Community Amplifiers Forum</ref>
== See also ==
* [[Transconductance]]
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* [http://www.idea2ic.com/LM13600/SpiceSubcircuit/LM13700_SpiceModel.html A more accurate LM13700 SPICE subcircuit]
* [http://www.alfarzpp.lv/eng/sc/AS13704.php AS13704], LM13700 functional replacement (without output buffers) by ALFA RPAR AS in [[SSOP24]] package.
* [https://www.muffwiggler.com/forum/viewtopic.php?t=65783 LM13700 - new discovery (at least for me)], Muff Wiggler forum, Aug 2012, discusses an error in the data sheet and why op-amps are usually favoured over the internal buffers.
[[Category:Linear ICs]]
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