**Test
Parameter** |
**Typ. Unit** |
**Typical Description** |

Input Bias Current |
µA |
Each input of
an operational amplifier has a certain amount of current that flows in or
out of it. This is basically the leakage current of the input transistor,
i.e., the base leakage current if the input transistor is bipolar, or the
gate leakage current if it is a FET. This current is known as the input
bias current, and is ideally zero.
Example of an
Actual Spec:
AD829: 3.3 µA
typ.; 7 µA max. |

Input Offset Current |
nA |
This is simply the mismatch or
difference between the input bias currents flowing through the inputs.
This is ideally zero.
Example of an
Actual Spec:
AD829: 50 nA
typ.; 500 nA
max. |

Input Offset Voltage |
mV |
An
ideal operational amplifier will give an output of 0V if both of its
inputs are shorted together. A real-world op amp will have a
non-zero voltage output even if its inputs are shorted together.
This is the effect of its input offset voltage, which is the slight
voltage present across its inputs brought about by its non-zero input
offset current. In essence, the input voltage offset is also the
voltage that needs to be applied across the inputs of an op amp to make
its output zero.
Example of an
Actual Spec:
AD712C: 0.1 mV typ.;
0.3 mV max. |

Open-Loop Gain |
V/mV |
This is the
ratio of the op amp's output voltage to its differential input voltage
without any external feedback.
Example of an
Actual Spec:
AD712: 150 V/mV
min.; 400 V/mV typ. |

Gain-Bandwidth Product |
MHz |
This is the
product of the op amp's open-loop voltage gain and the frequency at which
it was measured.
Example of an
Actual Spec:
AD829: 750 MHz
for Vs=+/-15V |

Slew Rate |
V/µsec |
This is the rate of
change of the op amp's voltage output over time when its gain is set to unity (Gain
=1).
Example of an
Actual Spec:
AD712: 16 V/µsec
min.; 20 V/µsec typ. |

Settling Time |
nsec |
This is the length of time for
the output voltage of an operational amplifier to approach, and remain
within, a certain tolerance of its final value. This is usually specified
for a fast full-scale input step.
Example of an
Actual Spec:
Settling time to 0.1% for a
10V step with Vs=+/-15V: 90
nsec |

Common Mode Rejection (CMR) |
dB |
This is the ability of an
operational amplifier to cancel out or reject any signals that are common
to both inputs, and amplify any signals that are differential between
them. Common mode rejection is the logarithmic expression of CMRR, i.e.,
CMR=20logCMRR. CMRR is simply the ratio of the differential gain to the
common-mode gain.
Example of an
Actual Spec:
AD829: 100 dB
min.; 120 dB
typ. |

Power Supply Rejection (PSR) |
dB |
PSR is a
measure of an op amp’s ability to prevent its output from being affected
by noise or ripples at the power supply. It is computed as the ratio of
the change in the power supply voltage to the change in the op amp's
output voltage (caused by the power supply change). It is often expressed
in dB.
Example of an
Actual Spec:
AD829: 98 dB
min.; 120 dB
typ. for Vs=+/-4.5V to +/-18V |

Phase Margin |
degrees |
An op amp will tend to oscillate at
a frequency wherein the loop phase shift exceeds -180°, if this frequency is
below the closed-loop bandwidth. The closed-loop bandwidth of a
voltage-feedback op amp circuit is equal to the op amp's
bandwidth at unity gain, divided by the circuit's closed loop gain.
The phase margin of an op amp circuit is the
amount of additional phase shift at the closed loop bandwidth required to
make the circuit unstable (i.e., phase shift + phase margin = -180°). As
phase margin approaches zero, the loop phase shift approaches -180° and
the op amp circuit approaches instability.
Typically, values of phase margin much less
than 45° can cause problems such as "peaking" in frequency response, and
overshoot or "ringing" in step response. In order to maintain conservative
phase margin, the pole generated by capacitive loading should be at least
a decade above the circuit's closed loop bandwidth.
Reference: www.analog.com
Example of an
Actual Spec:
AD847: 50 degrees
AD829: 60 degrees |

Input Voltage
Range, Common Mode |
V |
This is the maximum voltage
(negative or positive) that can be applied at both inputs of an
operational amplifier at the same time, with respect to the ground.
Examples of Actual Specs:
AD712: +14.5V,
-11.5 V typ. for Vs=+/-15 V;
AD844: +/- 10V
for Vs=+/-15 V |

Input Voltage
Range, Differential |
V |
This is the maximum voltage
(negative or positive) that can be applied across the two inputs of an
operational amplifier.
Example of an
Actual Spec: AD712: +/-20V |

Output Voltage Swing |
+/-V |
This is the maximum output voltage
that the op amp can deliver without saturation or clipping for a given
load and operating supply voltage.
Example of an
Actual Spec:
+/-11V min.;
+/-13V typ. for R=1K; Vs=+/-15V |

Input Resistance
or Impedance, Differential |
MW |
This is the
small-signal resistance between the two inputs (both ungrounded) of an op
amp.
Example of an
Actual Spec:
OP27C:
0.7 MW
min.; 4 MW
typ. |

Input Resistance
or Impedance, Common Mode |
GW |
Each input of
an op amp has a resistance with respect to ground. The common mode input
resistance of an op amp is the equivalent resistance value of the op amp's
two input resistances in parallel. This is the resistance of the two
inputs shorted together with respect to ground.
Example of an
Actual Spec:
OP27C: 2
GW
typ. |

Output Resistance
or Impedance |
W |
This is the
small-signal resistance or impedance between the output of an op amp and
ground.
Example of an
Actual Spec: AD844: 15
W
typ.,
open loop |

Power Supply Range |
V |
This refers to the minimum and
maximum values of supply voltages that the negative and positive supplies
of an operational amplifier can accept.
Example of an
Actual Spec:
AD712: +/- 4.5V min.; +/-18V max. |

Quiescent Current |
mA |
This is the
non-signal power supply current that the op amp will consume within a
specified power supply voltage operating range.
Example of an
Actual Spec:
AD712: 5 mA typ.;
6.8 mA max. for Vs=+/-15V |

Total Power
Dissipation |
mW |
The total DC
power supplied to the op amp minus the power delivered by the op amp to
its load.
Example of an
Actual Spec:
OP27: 90-100 mW
typ.; 140-170 mW max. |