suggest an opamp

[aruna1]

Hi I'm looking for an op amp for my ultrasonic receiver circuit

single supply, can handle 40khz dual op amp
and should be common.

any suggestions?

 

[ronv]

Maybe a TL082. Widely used I think.

 

[aruna1]

it is not single supply op amp.
I know it can be use with single supply using a virtual ground,but that requires at least 12v single supply.

 

[ronv]

Here is a page of rail to rail op amps.
Op Amps

 

[audioguru]

Texas Instruments says that the minimum supply for a TL072 or TL082 dual opamp is 7V.
I have used very many TL072 dual opamps powered from a single 9V battery and they all work perfectly when the battery voltage drops to 6.0V. Since they have Jfet inputs with an extremely high input resistance then the "virtual ground circuit" is just two or three resistors and a filter capacitor.
Of course the input, output and feedback to ground need coupling capacitors with a single-polarity supply.

 

[aruna1]

Texas Instruments says that the minimum supply for a TL072 or TL082 dual opamp is 7V.
I have used very many TL072 dual opamps powered from a single 9V battery and they all work perfectly when the battery voltage drops to 6.0V. Since they have Jfet inputs with an extremely high input resistance then the "virtual ground circuit" is just two or three resistors and a filter capacitor.
Of course the input, output and feedback to ground need coupling capacitors with a single-polarity supply.

Hi audio guru.I have several questions.

1. what i understand from data sheet of TL072 is that it requires minimum +7V and -7V supply to operate..that means 14V in single supply. So how did you operate it with 6V single supply? (+3V and -3V)
   
2. can you explain this virtual ground circuit you described? can you please post a schematic with all necessary components included?
   
3. when we use opamps with FET inputs do we have to use bleeding resistors with FET inputs as we do when we use discreet FETs?

Thank you very much

 

[audioguru]

1. what i understand from data sheet of TL072 is that it requires minimum +7V and -7V supply to operate..that means 14V in single supply. So how did you operate it with 6V single supply? (+3V and -3V)

ANY opamp will work from a single-polarity supply if its inputs are biased near half the supply voltage and coupling capacitors are used.
The datasheet for the TL072 shows two graphs with plus and minus 5V (or a single 10V supply) and one graph with the supply going as low as plus and minus 3.5V (or a single 7V supply).

2. can you explain this virtual ground circuit you described? can you please post a schematic with all necessary components included?

It is on a STICKY here https://www.electro-tech-online.com/threads/basic-opamp-circuits.35258/ .

3. when we use opamps with FET inputs do we have to use bleeding resistors with FET inputs as we do when we use discreet FETs?

I don't know what is a "bleeding resistor". The input of an opamp MUST have a DC voltage reference that can be supplied by a very high resistor value to the input of a Jfet.

 

[aruna1]

ANY opamp will work from a single-polarity supply if its inputs are biased near half the supply voltage and coupling capacitors are used.
The datasheet for the TL072 shows two graphs with plus and minus 5V (or a single 10V supply) and one graph with the supply going as low as plus and minus 3.5V (or a single 7V supply).

is it true for TL082 also?

It is on a STICKY here https://www.electro-tech-online.com/threads/basic-opamp-circuits.35258/ .

thank you I will check

I don't know what is a "bleeding resistor". The input of an opamp MUST have a DC voltage reference that can be supplied by a very high resistor value to the input of a Jfet.

bleed resistor is resitor used to discharge the gate capacitance of a FET like explained here

 

[audioguru]

is it true for TL082 also?

A TL072 is a TL082 selected for low noise (hiss).

bleed resistor is resitor used to discharge the gate capacitance of a FET like explained here

Usually you never connect the input of an opamp to its negative supply voltage. An opamp is not a switch, it is a linear amplifier so its input needs a DC reference voltage which is usually near half the supply voltage.