Buffer circuits?

[Ron J]

All,

Merry Christmas and a Happy New Year!

I was looking through some sensors on Digikey. Some of the ratings are
given at a certain load. For instance, 50 mV at 1 k-ohm. If I wanted to
bump this voltage a bit higher, can I use the following op amp buffer
ckt?

The sensor output is connected to 1 k-ohm resistor with one resistor
terminal connected to the non-inverting op amp input and the other
terminal is grounded. The opamp output is looped back to the inverting
input using a low loss piece of wire. The opamp output is then
connected to my measurement device.

Will this type of circuit work accurately with little deviation from
the original voltage input at the opamp?

I was thinking of all the losses that is encountered from the input of
the opamp to its output. My main concern is that since the output
deviation of the sensor only goes up to 50 mV at 1k-ohm, then noise
might affect it significantly compared to a higher output voltage,
right?

Thanks!

 

[Charles Schuler]

All,

Merry Christmas and a Happy New Year!

I was looking through some sensors on Digikey. Some of the ratings are
given at a certain load. For instance, 50 mV at 1 k-ohm. If I wanted to
bump this voltage a bit higher, can I use the following op amp buffer
ckt?

The sensor output is connected to 1 k-ohm resistor with one resistor
terminal connected to the non-inverting op amp input and the other
terminal is grounded. The opamp output is looped back to the inverting
input using a low loss piece of wire. The opamp output is then
connected to my measurement device.

Will this type of circuit work accurately with little deviation from
the original voltage input at the opamp?

I was thinking of all the losses that is encountered from the input of
the opamp to its output. My main concern is that since the output
deviation of the sensor only goes up to 50 mV at 1k-ohm, then noise
might affect it significantly compared to a higher output voltage,
right?

Well, you said you wanted some gain, so why not use a 10 k ohm feedback
resistor instead of a piece of wire? That would give you a voltage gain of
10. The non-inverting op-amp input is often grounded through a resistance
equal to the parallel equivalent of the input and feedback resistors (to
minimize offset error).

 

[Charles Schuler]

Well, you said you wanted some gain, so why not use a 10 k ohm feedback
resistor instead of a piece of wire? That would give you a voltage gain
of 10. The non-inverting op-amp input is often grounded through a
resistance equal to the parallel equivalent of the input and feedback
resistors (to minimize offset error).

I should have mentioned that the signal is fed to the inverting input with a
1 k ohm resistor.

 

[Jasen Betts]

All,

Merry Christmas and a Happy New Year!

I was looking through some sensors on Digikey. Some of the ratings are
given at a certain load. For instance, 50 mV at 1 k-ohm. If I wanted to
bump this voltage a bit higher, can I use the following op amp buffer
ckt?

The sensor output is connected to 1 k-ohm resistor with one resistor
terminal connected to the non-inverting op amp input and the other
terminal is grounded. The opamp output is looped back to the inverting
input using a low loss piece of wire. The opamp output is then
connected to my measurement device.

Will this type of circuit work accurately with little deviation from
the original voltage input at the opamp?

Yes. at low frequencies (DC to about 1KHz is excellent) higher frequencies
depend on the op-amp.

I was thinking of all the losses that is encountered from the input of
the opamp to its output. My main concern is that since the output
deviation of the sensor only goes up to 50 mV at 1k-ohm, then noise
might affect it significantly compared to a higher output voltage,
right?

yes. you can get some gain from that buffer circuit by using a 1K resistor
from the inverting input to ground an a 10K from the output to the inverting
input

That'll amplify the input 11 times so your signal is 550mV want more?
increase the 10K.