[sdiy] Negative content on half wave rectifier

[Harry Bissell]

for proper use of a capacitor the circuit of figure 4 is the only
one that works correctly.  In figure 6 the cap works on the
inverting input but not the non-inverting input. In Fig.4 the
last opamp is actually just an inverting summer so the cap works
equally well on both polarities...

ymmv. I have used all these circuits and been burned if I wanted to add a cap. You could
always add a low-pass filter (RC or otherwise) at the output of any of these.

H^) harry

----- Original Message -----
From: David G Dixon <dixon at mail.ubc.ca>
To: 'Justin Owen' <juzowen at gmail.com>, 'SDIY List' <synth-diy at dropmix.xs4all.nl>
Sent: Fri, 22 Jul 2011 12:51:16 -0400 (EDT)
Subject: Re: [sdiy] Negative content on half wave rectifier

> I was recently warned off using a single 1N4001 as a half 
> wave rectifier so I started playing with op-amp based 
> versions. I settled on the 'Improved Precision Half Wave 
> Rectifier' in Fig. 3 here: 
> http://sound.westhost.com/appnotes/an001.htm
> 
> ...snip...

I know you fixed the problem already, cuz I read ahead a few emails.
However, I just wanted to say that I've used both Figure 3 and Figure 6
circuits.  I like them both for different reasons.  For saw or triangle
shaping, it's important to add the suggested cap to minimize the glitch.
It's also important to add a cap across the feedback loop of the final
opamp.

In any case, both of these HWR circuits work perfectly.

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-- 
Harry Bissell & Nora Abdullah 4eva