Operational Amplifier Selection and Requirements

fish001

Operational Amplifier Selection and Requirements [Copy link]

1. Common-mode input resistance (RINCM) This parameter indicates the ratio of the input common-mode voltage range to the change in bias current within this range when the operational amplifier operates in the linear region.

2. DC common mode rejection (CMRDC) This parameter is used to measure the operational amplifier's ability to suppress the same DC signal acting on both input terminals.

3. AC common-mode rejection (CMRAC) CMRAC is used to measure the operational amplifier's ability to suppress the same AC signal acting on both input terminals. It is a function of the differential open-loop gain divided by the common-mode open-loop gain.

4. Gain Bandwidth Product (GBW) The gain bandwidth product AOL is a constant that defines the region in the open-loop gain versus frequency characteristic curve where it rolls off at -20dB/decade.

5. Input bias current (IB) This parameter refers to the average current flowing into the input terminal when the operational amplifier operates in the linear region.

6. Input bias current temperature drift (TCIB) This parameter represents the change in input bias current when the temperature changes. TCIB is usually expressed in pA/°C.

7. Input offset current (IOS) This parameter refers to the difference between the currents flowing into the two input terminals.

8. Input offset current temperature drift (TCIOS) This parameter represents the change in input offset current when the temperature changes. TCIOS is usually expressed in pA/°C.

9. Differential input resistance (RIN) This parameter represents the ratio of the change in input voltage to the corresponding change in input current. The change in voltage causes the change in current. When measuring at one input terminal, the other input terminal is connected to a fixed common-mode voltage.

10. Output impedance (ZO) This parameter refers to the internal equivalent small signal impedance at the output end when the operational amplifier operates in the linear region.

11. Output voltage swing (VO) This parameter refers to the peak-to-peak value of the maximum voltage swing that can be achieved when the output signal is not clamped. VO is generally defined under a specific load resistance and power supply voltage.

12. Power consumption (Pd) indicates the static power consumed by a device at a given power supply voltage. Pd is usually defined under no-load conditions.

13. Power Supply Rejection Ratio (PSRR) This parameter is used to measure the ability of an operational amplifier to keep its output unchanged when the power supply voltage changes. PSRR is usually expressed as the change in input offset voltage caused by a change in power supply voltage.

14. Conversion rate/slew rate (SR) This parameter refers to the maximum value of the ratio of the change in output voltage to the time required for this change. SR is usually expressed in V/μs, and sometimes also expressed as positive and negative changes.

15. Power supply current (ICC, IDD) This parameter is the static current consumed by the device at a specified power supply voltage. These parameters are usually defined under no-load conditions.

16. Unity gain bandwidth (BW) This parameter refers to the maximum operating frequency of the operational amplifier when the open-loop gain is greater than 1.

17. Input offset voltage (VOS) This parameter indicates the voltage difference required to be applied to the input terminal to make the output voltage zero.

18. Input offset voltage temperature drift (TCVOS) This parameter refers to the change in input offset voltage caused by temperature change, usually expressed in units of V/°C.

19. Input Capacitance (CIN) CIN represents the equivalent capacitance of any input terminal when the operational amplifier operates in the linear region (the other input terminal is grounded).

20. Input voltage range (VIN) This parameter refers to the range of input voltage allowed when the operational amplifier is working normally (the expected results can be obtained). VIN is usually defined under the specified power supply voltage.

21. Input Voltage Noise Density (eN) For operational amplifiers, the input voltage noise can be viewed as a series noise voltage source connected to any one of the input terminals. eN is usually expressed in nV/root Hz and is defined at a specified frequency.

22. Input Current Noise Density (iN) For operational amplifiers, input current noise can be considered as two noise current sources, connected to each input terminal and the common terminal, usually expressed in pA/root Hz, defined at a specified frequency.