Operational Amplifiers. Benchmark Companies Inc PO Box 473768 Aurora CO 80047. What is an Op-Amp?. INTRODUCTION What is an operational amplifier?
Benchmark Companies Inc
PO Box 473768
Aurora CO 80047
What is an operational amplifier?
In this chapter, we will define what an operational amplifier is, and discuss the many parameters that distinguish one type of device from another.
channel separationclosed-loop gaincommon-mode rejection ratiogain-bandwidth productinput bias Current offsetinput offset Currentinput offset voltageInput resistance
input voltage range
output voltage swing
This is the maximum positive and negative voltage that can be used to power the op-amp.
This is the maximum power that the op-amp is capable of dissipating, given a specified ambient temperature (i.e., 500 mW @ <75C).
This is the maximum voltage that can be applied across the + and - inputs.
This is the maximum input voltage that can be simultaneously applied between both inputs and ground, also referred to as the common-mode voltage. In general, this maximum voltage is equal to the supply voltage.
This is the ambient temperature range for which the op-amp will operate within the manufacturer’s specifications. Note that the military grade version (741) has a wider temperature range than the commercial, or hobbyist, grade version (741C).
This is the amount of time that the op-amp’s output can be short-circuited to ground or either supply voltage.
This is the voltage that must be applied to one of the input terminals to give a zero output voltage. Remember, for an ideal op-amp, the output voltage offset is zero!
This is the average of the currents flowing into both inputs. Ideally, the two input bias currents are equal.
This is the difference of the two input bias currents when the output voltage is zero.
This is the range of the common-mode input voltage (i.e., the voltage common to both inputs and ground).
This is the resistance “looking in” at either input with the remaining input with the remaining input grounded.
This is the resistance seen “looking into” the op-amp’s output.
This is the maximum output current that the op-amp can deliver to a load.
Depending on the load resistance, this is the maximum peak output voltage that the op-amp can supply without saturation or clipping.
This is the ratio of the output to input voltage of the op-amp without external feedback.
This is the ratio of the maximum voltage swing to the change in the input voltage required to drive the output from zero to a specified voltage (e.g., ±10 volts).
This is the time rate of change of the output voltage with the op-amp circuit having a voltage gain of unity (1.0).
This is the current that the op-amp will draw from the power supply
This is a measure of the ability of the op-amp to reject signals that are simultaneously present at both inputs. It is the ratio of the common-mode input voltage to the generated output voltage, usually expressed in decibels (dB).
Whenever there is more than one op-amp in a single package, such as a type 747 op-amp, a certain amount of “crosstalk” will be present. That is, a signal applied to the input of one section of a dual op-amp will produce a finite output signal in the remaining section, even though there is no input signal applied to the unused section.
AL = AOL/ACL
BW= 0.35/rise time