Sample and Hold

[redepoch7]

I was looking for a simple way to make a sample and hold circuit.

I came across this...
**broken link removed**

I understand that the IC is a voltage follower.

Could I build one of those with a simple op-amp and substitute it in?

The goal of the project is to have an input of either some random/noise or some other input and get that really cool sample and hold synth sound.

 

[bychon]

The LM102 IS a simple op-amp. I don't know why you would want to substitute an op-amp for an op-amp and think that's "simpler".

The problem is that this circuit only holds a momentary voltage. One voltage. It doesn't sample sounds and hold a few seconds of them. It just outputs the DC level that was present at the moment the sample command pulse went to negative 15 volts. It won't even pass audio frequencies because the capacitor tries to average them into a DC level.

 

[redepoch7]

I know that much. but if the voltage is controling the frequency as in a Voltage controlled oscillator then you can get some really cool random beeps and blips.

That's all I'm trying to do and I'd like to attempt it with the parts I have instead of ordering parts I don't.

I had read that, yes it is an op-amp, the LM102 is a voltage follower. That was taken from the datasheet that I found online. Isn't a voltage follower just another application of an op-amp?

I'm only just learning about all this so don't quote me on anything.

So, anyone know of a simple way to make a sample and hold circuit?

 

[mneary]

So, anyone know of a simple way to make a sample and hold circuit?

We seem to be going around in circles. The circuit that you posted is the simplest sample and hold circuit that most of us will ever see. You can use almost any op amp in place of the LM102, such as TL074, LM324, etc. depending on what you have. You can use a lot of different JFETs. I see a lot of J310, MPF102, 2N3819, etc. The diode can be anything small, like 1N914/1N4148. The capacitor should have a low loss dielectric, preferably Mylar or poly, never electrolytic or ceramic.

That's all I'm trying to do and I'd like to attempt it with the parts I have instead of ordering parts I don't.

Hopefully the parameters I gave above provide enough flexibility to find something. If not, you could assemble a short list of your op amps, diodes, and JFETs and we can help further.

 

[JimB]

The goal of the project is to have an input of either some random/noise or some other input and get that really cool sample and hold synth sound.
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if the voltage is controling the frequency as in a Voltage controlled oscillator then you can get some really cool random beeps and blips

I cant help but think that you misunderstand the operation of this sample and hold circuit.

The circuit is intended to hold a fixed DC value for some period of time.
For example if a varying voltage is to be measured, it is difficult to do that with a dvm, by sampling and holding the voltage, ie freezing that voltage in the sample and hold circuit, the DVM can then take its time and read the voltage correctly.

This circuit cannot produce beeps and blips.

JimB