[sdiy] Dual 914 diode in a SOT-23 package?

[Harry Bissell]

The circuit that you have drawn is suitable for DC and near DC uses. like for a control voltage. Its really
NOT good for audio rate circuits where the leakage and parasitic capacitance will cause trouble. The diodes across
the inputs rely on the opamp being fast enough to make the negative input follow the positive input... not always true with
fast moving cignals.

Now someone just posted an EXCELLENT link about how to handle protective components but i don't remember who... :^(

H^) harry

----- Original Message -----
From: Justin Owen <juzowen at gmail.com>
To: SDIY List <synth-diy at dropmix.xs4all.nl>
Sent: Tue, 13 Mar 2012 05:16:22 -0400 (EDT)
Subject: Re: [sdiy] Dual 914 diode in a SOT-23 package?

Hi Neil,

>> The diodes will be used as per this schematic:
http://www.sdiy.org/juz/euro_input_detail_02.pdf

>I don't remember seeing that particular combination.  Anyway, I would  
remove D10 and D11

Why is that? Op Amp Cook Fig. 3.13 shows it as Common-Mode Input Protection.

>and D8 and D9 must be low-leakage types,  
definitely not 1N914.  Otherwise you'll likely get horrible non- 
linear behaviour.  See section 3.2.1 of IC Op-Amp Cookbook for examples.

I'm looking at Fig. 3.12 and it definitely has 914s listed.

I am using a first edition of that book though....

Not disagreeing with you - just asking for clarification. The last time we had this thread it did kind of end up as a three way tie so I know there's some different opinions on this matter.

Cheers,

J







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-- 
Harry Bissell & Nora Abdullah 4eva