Single Ended and Differential Opamp

Thread Starter

alexfrey

Joined Feb 23, 2019
22
Being a single ended or differential for opamp depends on type of device or just wiring ? I mean whether the opamp is same but our wiring makes it single ended or differential ? or opamp type makes it single ended or differential ? for example if I wire - of an opamp to ground it will be single ended if I don't it will be differential. Is it like that ?

Thanks in advance.
 

Thread Starter

alexfrey

Joined Feb 23, 2019
22
Hi Eric,
Thanks for respond. The document seems to be very useful but since I am a new automation engineer(not being good at electronic) I think I couldn't find the answer of question above.
Just the respond to question above will help me understand wiring of analog inputs.
Regards,
 

kubeek

Joined Sep 20, 2005
5,752
You can also have an opamp with differential output like AD8138. The input can then be configured either as single ended or differential.
 

MrChips

Joined Oct 2, 2009
23,286
Differential input or differential output?
As @kubeek has pointed out, there are opamps that are available with differential outputs.

By definition, operational amplifiers have differential inputs, i.e. they amplify the voltage difference between the two inputs.
You can fix the voltage reference of either input to turn it into a single ended input amplifier.
 

OBW0549

Joined Mar 2, 2015
3,566
Being a single ended or differential for opamp depends on type of device or just wiring ? I mean whether the opamp is same but our wiring makes it single ended or differential ? or opamp type makes it single ended or differential ? for example if I wire - of an opamp to ground it will be single ended if I don't it will be differential. Is it like that ?
I think the key to ending your confusion is to make a distinction between opamps and opamp circuits.

Opamps themselves have inputs that are inherently differential; that is, the opamp's output responds to the voltage difference between its two inputs. However, their gain factor (e.g., the ratio of output voltage change to input differential voltage change) is extremely high, anywhere from a couple thousand to hundreds of millions, varies wildly with temperature, and is different from one unit to the next.

Opamp application circuits seek to use the opamp's high open-loop gain along with feedback through discrete components to create a controlled input-output relationship which is determined by the feedback components rather than the characteristics of the opamp. And the opamp application circuit can be arranged to function in either single-ended or differential fashion, as desired.
 

Thread Starter

alexfrey

Joined Feb 23, 2019
22
I think the key to ending your confusion is to make a distinction between opamps and opamp circuits.

Opamps themselves have inputs that are inherently differential; that is, the opamp's output responds to the voltage difference between its two inputs. However, their gain factor (e.g., the ratio of output voltage change to input differential voltage change) is extremely high, anywhere from a couple thousand to hundreds of millions, varies wildly with temperature, and is different from one unit to the next.

Opamp application circuits seek to use the opamp's high open-loop gain along with feedback through discrete components to create a controlled input-output relationship which is determined by the feedback components rather than the characteristics of the opamp. And the opamp application circuit can be arranged to function in either single-ended or differential fashion, as desired.
Thanks for respond. As I understand from your respond. There is just one type of opamp ( I mean no distinction as single ended or differential) and my circuit makes it single ended or differential ?
 

Thread Starter

alexfrey

Joined Feb 23, 2019
22
I have a question about wiring analog input and measuring method.

It seems to me;

  • 2 and 3 wire current analog input wiring is single ended measuring and is going to an amplifier in module that is single ended.

  • 4 wire current analog input wiring is differential measuring and is going to an amplifier in module that is differential.

  • Voltage input wiring is also same with 4 wire current which is differential.
My thinking is right or I am missing something ?

Thanks in advance.
 
Top