It must be within these parameters:
0 to 48 volt DC ( I can regulate the voltage down using a zener diode).
Maximum 10 milliamperes total current draw.
DIP-8 package.
Minimum self noise. Good common mode noise rejection.
Usage: Amplifier and impedance buffer for piezoelectric elements wired in balance.
Why a impedance buffer is needed:
The problem with piezo guitar pickups and piezoelectric crystals is that they are not well matched to typical audio inputs. By their nature they can generate a lot of signal, but they cannot drive a 50 kilohm typical line input. The pickup needs to work into a much higher impedance, typically 1 megohm or so.
So what to people do? They go and plug a piezoelectric disks output directly into the line input of their recorder, typical impedance 50k, or the plug-in-power mic input of their recorder, typical impedance about 7k, and they start to bitch and moan that this damn thing sounds tinny. Which is does ! But they don't understand why!
The reason why these devices often sound tinny is because the piezo sensor presents its signal through a series capacitance which is small, typically 15nF or less. When wired to a normal 50 kilohm line input this forms a high-pass filter, which eliminates the bass.
0 to 48 volt DC ( I can regulate the voltage down using a zener diode).
Maximum 10 milliamperes total current draw.
DIP-8 package.
Minimum self noise. Good common mode noise rejection.
Usage: Amplifier and impedance buffer for piezoelectric elements wired in balance.
Why a impedance buffer is needed:
The problem with piezo guitar pickups and piezoelectric crystals is that they are not well matched to typical audio inputs. By their nature they can generate a lot of signal, but they cannot drive a 50 kilohm typical line input. The pickup needs to work into a much higher impedance, typically 1 megohm or so.
So what to people do? They go and plug a piezoelectric disks output directly into the line input of their recorder, typical impedance 50k, or the plug-in-power mic input of their recorder, typical impedance about 7k, and they start to bitch and moan that this damn thing sounds tinny. Which is does ! But they don't understand why!
The reason why these devices often sound tinny is because the piezo sensor presents its signal through a series capacitance which is small, typically 15nF or less. When wired to a normal 50 kilohm line input this forms a high-pass filter, which eliminates the bass.
I think you will get what you want if you select an opamp with FETs at the input pins. Either a JFET opamp like OPA604, or a MOSFET opamp like OPA1656. Pull up their datasheets to see the strengths and weaknesses of each. I bet you are most interested in current noise (femtoAmps per root Hertz) for such high impedance sources. That's inside the datasheet but seldom on the front page.
There are fewer than ten opamp chips that can accept 48V power supplies, and none of them are especially low noise, so plan on building a voltage regulator. If you regulate to 30V the universe of possible opamps is much much larger.
There are fewer than ten opamp chips that can accept 48V power supplies, and none of them are especially low noise, so plan on building a voltage regulator. If you regulate to 30V the universe of possible opamps is much much larger.
Ok! I am mostly using TLO82 op amps in my designs that is open source.
Those are here: GitHub - Supermagnum/piezoelectric: A write-up with links to different versions of impedance buffer and amplifiers for piezoelectric elements.
Those are here: GitHub - Supermagnum/piezoelectric: A write-up with links to different versions of impedance buffer and amplifiers for piezoelectric elements.
They are within the voltage range I specified.
As you clearly can observe, I am running them at 11 volts.
double-gain/double-gain.pdf at main * Supermagnum/double-gain * GitHub
As you clearly can observe, I am running them at 11 volts.
double-gain/double-gain.pdf at main * Supermagnum/double-gain * GitHub
Clearly my *ss
That page contains **47** files, are we supposed to open all of them and find one stating Op Amps are fed +/- 11v?????
47 files from:
double-gain/Connector.dcm at main * Supermagnum/double-gain * GitHub
to
double-gain/fp-lib-table at main * Supermagnum/double-gain * GitHub
Get real.
Common practice is to post schematic here in picture form, alliviates confusions and sore feelings.
If you have 11V for the OPAMP, why ask for an OPAMP that can run on 48V? Very few can, and modern OPAMPS usually handle <12V.
I'd use a simple JFET buffer in front of your favorite OPAMP. Done. You only need a few volts signal swing out, so if you drop your circuit voltage to 9V, you can even have the option of running on a 9V battery...unless you need 48V to bias the piezo transducer? If running on <10V you have many OPAMPS to select.
If you have 11V for the OPAMP, why ask for an OPAMP that can run on 48V? Very few can, and modern OPAMPS usually handle <12V.
I'd use a simple JFET buffer in front of your favorite OPAMP. Done. You only need a few volts signal swing out, so if you drop your circuit voltage to 9V, you can even have the option of running on a 9V battery...unless you need 48V to bias the piezo transducer? If running on <10V you have many OPAMPS to select.
+/-18V max is standard for opamps, which is practice means +/-15V so they run cooler and last longer. You don't have dual rails (is this phantom power 48V by any chance? If so you should have made this clear, not force guesswork...)
Yes, you can use a zener to drop the voltage, but zeners are noisy so use a large cap across it. You'll need a virtual ground if running from phantom power, another zener and capacitor possibly. Note that if it is phantom power the 6k8 resistors mean a 4mA load will only see about 34V.
OPA1652 JFET dual opamp is 2mA per channel and good overall specs for instance, 10pA bias current and 3fA/√Hz current noise should handle high impedances nicely. Just an example of a JFET opamp that I happen to have been using recently in phantom powered microphone circuit as it happens.
NOBODY does that, you are making up a "problem" so you can show your wonder solution.
Nobody connects a raw Piezo straight to a mixer Line in.