Why a resistor is connected between non inverting terminal and ground.

AlbertHall

Joined Jun 4, 2014
12,328
To 'cancel out' the effects of the amp input bias currents. the resistor to ground would have a value equal to the value of the other two resistors in parallel so the bias current would drop the same voltage on both inputs thus removing extra input offset voltage.
 

GopherT

Joined Nov 23, 2012
8,009
Why a resistor is connected between non inverting terminal and ground.
Please find the attachment.
The output is the difference between - and + inputs multiplied by the gain of the inverting amplifier. If there is NO connection to + input, then there is no way for the amplifier to reference the difference between the inputs. Note, the + input can be connected to other voltages and the output will change based on the gain and difference between the two inputs.

If you are asking about the value of the resistor, then the answers above should suffice for bipolar op amps. Current should be limited match the input current seen by the - input (calculate as the parallel resistance of the feedback resistor and input resistor connected to the - input). This will minimize input offset.

In general, the resistor can be replaced by a bare wire connection on an op amp with jFET input because the input current flow is so low on these devices.
 
Top