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Peak Detector: A Classic Analog Circuit Still in Wide Use

Bill Schweber
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Dave1010101
Dave1010101
6/12/2014 9:47:36 AM
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Newbie
Re: Precision Monolithics
Yes the PKD-01 was a quite nice chip. Internal to Preciscion Monolithics there was quite a political battle about whether the PKD-01 or GAP-01 was going to be the better revenue generator.

Marketing favored the PKD-01 and engineering the GAP-01.

Glad you liked it.

 

 

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Kev1
Kev1
6/12/2014 5:05:00 AM
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Re: Precision Monolithics
Hi Dave, just to say I used the PKD-01 in the distance past, a great little chip and at the time beat the competition on it's versatility.

We were very sad at the time it was announced that production was to end, we were kindly supplied with some last production run chips for spares, but they were never required. Probably still in my 'misc' drawer...

This is one of the chips that I will always remember, in fact that's how I found your post, just surfing to see if they still get a mention!

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RedDerek
RedDerek
12/31/2013 4:55:57 AM
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Master
Classic building blocks
Hmm,

1. Depletion MOSFET configured as a self-limiting circuit.

2. Multipliers - reason that should be soon blogged about.

Others mentioned thus far are all good old basics as well.

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mediatechnology
mediatechnology
12/11/2013 5:08:14 PM
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Newbie
Level Detectors Absolute Value, Peak and RMS
I have a forum thread "Level Detectors Absolute Value, Peak and RMS" that many of you may find interesting. It contains a number of diode-based Design Ideas collected over the years as well as the classic Blackmer RMS detector and comparator-based peak detectors. I do remember the PMI GAP-01 and PKD-01 and one of the posts contains some applications.


The link is here: http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=111

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Bill_Jaffa
Bill_Jaffa
12/11/2013 4:54:19 PM
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Blogger
Re: Peak Detector
Good points about reset and other aspects--I was just trying to capture the "essence" in that basic schematic. As with all real circuits, there are always more things you need to add in the final design, of course.

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pmoyle111
pmoyle111
12/11/2013 4:08:30 PM
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Newbie
Peak Detector
For completeness, the circuit is actually missing the reset which would be a fet or analog switch across the cap. Otherwise you can no longer detect any other peaks except those greater than the last one.


To make an enveope follower, a resistor is just placed across the cap where the rc time constant is relative to what's inside the envelope so that the cap is naturally discharged as the signal falls.

In the case of the crystal radio, there should be a small cap across the output. As I remember something like an .02 uF mica, this along with the resistance of the headphones made the envelpe follower.

The envelope follower was very commonly used in AGC circuits back in the day.

Back about 20 yr ago I used the PDK01 in a couple of custom instrument designs. The "good old days".

 

 

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vvc
vvc
12/11/2013 3:28:04 PM
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Newbie
Other Tried and True Analog Circuits
A couple of very important analog circuits still widely used today in most anything requiring a frequency source are the Colpitts and Hartley oscillator topologies. Another circuit which is ubiquitous in most analog circuits is the differential amplifier found in the majority of operational amplifier IC's (as illustrated in the gain elements of your peak detector).

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Victor Lorenzo
Victor Lorenzo
12/8/2013 3:52:54 PM
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Crystal radios... ohhhh....
@Bill: "A relative of the peak detector is the crystal (diode) radio", I should admit it, I played a lot with them and tried lots of different diode types trying to find 'the best' diode for the circuit. At first I only used the Antenna+LC+Diode+Headphones, and soon started putting some germanium type transistors here-and-there. I was only 11 or 12 year old, but my father had everything I needed (tons of passive components, tubes transistors, old radios for salvaging) for those little projects (including lots of books!)

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Victor Lorenzo
Victor Lorenzo
12/8/2013 3:42:39 PM
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Analog vs Digital? Why not better Mixed?
@Bill, "After all, wouldn't it make more sense to use an ADC on the signal of interest, with a basic software loop checking the newest converted value against the previous ones?" There're several algorithms for implementing the peak detector in the digital domain for real-time applications but it some times gets a little bit tricky, not so obvious I would say, as things are not processed 'in a loop'.

I fully agree with you at "the ADC has to sample at much higher than the Nyquist rate" and, if you let me, I would add that the 5xNyquist criteria that usually serves for being able to record/reproduce analog signals with acceptable quality is still short for this application. You may lose important events present in the analog signal.

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eafpres1
eafpres1
12/8/2013 3:11:30 PM
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Blogger
Re: Rectifier circuit
Some other examples using traditional full wave rectifier are AC-AC power converters used in motor drives.  Some of these include a transformer in the output stage as isolation, even if the voltage isn't transformed.

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