This is a part from a (severely amateurish) Piezoelectric transducer amplifier circuit. I
am looking to identify this diode so that I can find a datasheet for it as well as possibly purchase more.

Diode picture

The original circuit PCB is shown below. I have drawn a schematic of the board (also below). Note that the marking in this circuit is of a zener diode; this is an error.

Op-amp circuit Schematic of example circuit


In the circuit you show (copied below) the diode can be replaced by a 1N4148 or 1N914 or any small signal diode.

BUT there should also be a small series resistor as, as shown the diode will load down the transducer on positive half cycles. Can you show us that circuit in its original context? Piezo transducers usually require "all the voltage they can get" and it is unlikely that the loading is intended.

The diode is shown as a Schottky (signified by the squared bars on the end of the cross line on the sysmbol) BUT that is probably due to the user choosing a symbol that was "about correct).

enter image description here

I'm surprised that you say that "it goes" as the circuit has either been designed by a grand master first class with honours or thrown together by someone who has a very poor understanding of how an op amp works. That's not meant to be rude - it's just that it would be a miracle if it works - so it it does it's either masterful or a product of advanced playing.

LM741 pinout below.

  • The LM741 is being operated from a 6V (low) single supply (far from rail to rail)

  • Circuit is negative rail referenced - LM741 is not rail top rail and results are highly unpredictable but tending towards death.

  • Pin3 non inverting input is ground referenced with no formal bias above ground. Input bias current in R2 and input offset voltage will set pin 3 at "unknown".

  • Vout/pin 6 to Vin_Inv/pin2 + R1 + piezo may make an oscillator and transitions of piezo below grund MAY provide comparator action from IC. Or not.


Change opamp to LM324 or LM358

Chnage pinouts to pins with same names on eg LM358.

Add 10k from pin 3 to B+

Add 10k to start in series with LED and diode.

Make diode shown a 1N4148 or similar.

Maybe add small cap across LED. (0.01 - 0.1 uF)

enter image description here

  • \$\begingroup\$ your comments are entertaining as well as informative. i now know more, and less. as always \$\endgroup\$ – yoshco Dec 4 '11 at 22:49

What you are saying doesn't add up. Yes, it is very likely a diode with the black stripe identifying the cathode end. However, if you know the specs then you can just get a diode that matches them. If you don't know the specs, then how do you know you want another one?

You say it "works", but how do you really know except for whatever conditions you have tested it with? Show the schematic it is in and give particularls like voltage of power supplies, expected currents, etc, and we can probably recommend a diode that will do.

For example, for basic hobby rectifier use for 50V or less, the very common and cheap 1N4001 will do fine. Same thing for up to 400V is 1N4004. However, your diode may be a zener, which makes things different. You could even be using it as a rectifier and not know of its zener characteristics.

All in all I would forget about this diode. If you don't know what you have, you basically don't have anything. Figure out the specs for what you really need and get a diode based on those.

  • \$\begingroup\$ Olin your comments are valid, above you can see the circuit im using. \$\endgroup\$ – yoshco Dec 4 '11 at 21:51
  • \$\begingroup\$ Edit the question to include the new information. Post necessary and important information in the question itself. You can't expect people to follow links except to get optional background info, like the datasheet of a part. \$\endgroup\$ – Olin Lathrop Dec 4 '11 at 22:44

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