Opamp Gain calculation!

[binu G]

Iam operating an opamp with single supply not with dual suply.
how i can calculate the gain?

i found in many books the derivation is given for the system with dual supply.
when i tried with those relation iam not able to find a value which match the pratical one.

can anyone correct me ?

thanks

binu g

 

[AartDeGeus]

it doesn't matter single or dual power supply.
gain = vout/vin

 

[chevron_guy]

aartdegeus is right, whether the opamp uses single or dual supply don't matter, as long as the supply is big enough that all the transistors works in it's desired region, the opamp should give reasonable gain..

 

[layes2]

do .dc analysis
and derive the output to input you get the gian

 

[mrm]

Carefully read Doc. number sboa092a downlodable from Texas Instruments.

 

[SkyHigh]

Hi binu G,

An Op-Amp gain is independent of the rail supply voltages, dual or single. It is the inherent Open-Loop Voltage Gain, Av = Vo/Vi. i.e. it is also the Differential Gain between the Inverting and the Non-Inverting Terminal. Such is a simple Comparator.

Dual Supply is usually used to provide a wider rail-to-rail bipolar voltage swing at the output, just as well as detection at the input, than a Single Supply.

A Single Supply can also provide bipolar voltage swing if the Non-Inverting Terminal is made as the crossing or reference voltage.

When you use a negative feedback path from output to the Inverting Terminal of the Op-Amp, the entire gain is only dependent on the external circuit components(capacitors and resistors). This gain is not the Open-Loop or the Op-Amp Differential Gain. It is the Op-Amp Circuit Gain, i.e. gain based on the external circuit.

External circuit is the feedback circuit and the bias circuit as a whole.

Added after 2 minutes:

To previous post, you can also use the Inverting Terminal as the crossing reference as well, depending what sort of detection you want to make.

 

[rongli]

I think you must add the bias voltage in single supply .so the gain is feasible.

 

[s_a_r_a]

When you design an op amp circuit using a single power supply or a double power supply, there are no differences in calcuting its transfer function or,simpler, its function.
The differences between the two ways to supply the op amp involves:
-the noise (normally in audio application is preferred to use double power supply
from the noise point of view)
-the output voltage swing(refer to the post of SkyHigh. I totally agree with him)

Regards.

 

[radigital]

Whether you opamp is power by single or dual supply, gain
can be calculated as follows:

Calculate the gain of each individual stage of the opamp as
follows: the product of transconductance (gm) of the main
amplifying device and output resistance (Ro) of the output
devices. Both these parameters can be found using
DC analysis in most of the tools. If the output node has
2 devices in parallel, find individual Ro`s and take their
parallel sum.

Multiply the gain of individual stages to get the overall
small signal gain. This is theoritical gain.

What you get by using Vout/Vin in DC analysis is
large-signal gain and is not small-signal gain.

However these theoretical calculations may or may
not be equal to the gain obtained from AC analysis.

--Radigital

 

[paladinzlp]

gain=vout/vin
on common gain=gm*rout

 

[uk]

you know for an opamp in ideal situation open loop gain is infinite. This infinite gain gives the benefit in closed loop topology. So don't matter the power supply is single or double. Do the same calculations.