[sdiy] Adapting exponential convertor for single supply

[houshu at muj.biglobe.ne.jp]

Hello Tom and list,

I don't follow all the thread.  But, I guess these designs may help you.

Single Supply Exponential Converters:
http://houshu.at.webry.info/200907/article_1.html

Modified to control LM13600 through current mirrors:
http://houshu.at.webry.info/201202/article_1.html
The current mirror input needs doubled Vbe.

I built a VCF with satisfactory result:
http://houshu.at.webry.info/201202/article_2.html

OSCar uses current mirrors in LM13600 as an exponential converter.
But my design is betrer (precise) at least on LTspice.

Don't require me to explain these tricky circuits. ;->

Sam HOSHUYAMA
Saitama, JAPAN

----- Original Message -----
From: "Tom Wiltshire" <tom at electricdruid.net>
To: "Synth-diy at synth-diy.org DIY" <Synth-diy at synth-diy.org>
Sent: Thursday, July 27, 2017 07:31:35
Subject: [sdiy] Adapting exponential convertor for single supply

Hi All,

What’s the simplest way to adapt this exponential convertor for a single supply (0-9V)?

http://imgur.com/ZhixiC7

Could I use a simple midpoint bias to act as the ground and expect it to work? It feels wrong, although I don’t know why.
Bumping the “grounds” up to a useful level with diodes feels better somehow, more like is done in this schematic:

https://hackadaycom.files.wordpress.com/2015/09/two_transistors_expo-sch.png

What would you recommend?

Thanks,
Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================


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