2. OPERATIONAL AMPLIFIER
An Operational Amplifier is basically a three-
terminal device which consists of two high
impedance inputs.
1.Inverting input
2.Non-inverting input
4. Ideal Op-Amp
An ideal op-
amp exhibits the
following
characteristics −
Input
impedance Zi=∞Ω
Output
impedance Z0=0Ω
Open loop voltage
gain Av=∞
5. Practical Op-Amp
A practical op-
amp exhibits the
following
characteristics −
Input impedance, Zi in
the order of Mega
ohms.
Output
impedance, Z0 in the
order of few ohms..
Open loop voltage
gain,Av will be high.
7. Operational Amplifiers: Key
Characteristics and Parameters
Open loop voltage gain:
Internal voltage gain of the device.
Represents the ratio of output to
input voltage when there are no external
components.
8. Operational Amplifiers: Key
Characteristics and Parameters
Input offset voltage: The input voltage is
differential dc voltage required between
the inputs to force the output to zero
volts.
range: 2m or less
Input bias current:The input bias current is
the dc current required by the inputs of
the amplifier to properly operate the first
stage.
Ibias= (I1+I2)/ 2
9. Operational Amplifiers: Key
Characteristics and Parameters
Common Mode Rejection Ratio:
The measure of an amplifiers ability to
reject common mode signals.
CMMR= Aol /Acm
The CMMR is often expressed in decibels
(db) as
CMMR= 20log(Aol /Acm)
10. Operational Amplifiers: Key
Characteristics and Parameters
Slew rate : the maximum rate at which the
output voltage of an op-amp can change.
Slew rate : ΔVout/Δt
Varies from o.5 v/µs to 35 v/µs
13. Voltage follower
The voltage-follower configuration is a special case of the non-
inverting amplifier where all of the output voltage is fed back to the
inverting input by a straight connection
15. COMPARATOR
Provides very fast
switching time.
Specialized op-amp
circuit that compares
two input voltage
and produce an
output that is always
either one of two
states, indicating the
greater or less than
relationship between
inputs.
16. SUMMING AMPLIFIER
It has two or more
inputs and its output
voltage is
proportional to the
negative of the
algebric sum of its
input voltages.
Output voltage,Vout =
-(Vin1+Vin2+Vin3+
……+VinN)
17. AVERAGING AMPLIFIER
A summing amplifier
can be made to
produce the
mathematical average
of the input voltages.
It is setting by the
Rf/Ri=1/n
