ESE 272 Laboratory 6
High, low, and bandpass ampli ers
Objec ves:
In this lab we will explore the basics of frequency selec ve ampli ers using opera onal
ampli ers.
Parts required:
• TLC2274A opera onal ampli er
• Resistors
• Capacitors
O set voltage:
Op amps are not perfect. We say that the output is zero when the voltage between the
inver ng and non-inver ng op amp inputs is zero. But, that is not perfectly true. To make
the output zero, there must be a ny voltage between the inver ng and non-inver ng
inputs due to imperfec ons in the matching of the input transistors. This voltage is called
the input o set voltage (VIO) and is a key metric of op amp performance.
The input o set for our TLC2274A op amp is given in the data sheet:
It is typically around 300 V at room temperature, but can be as high as 1.5 mV over the
whole temperature range. They specify the o set voltage magnitude, but not its
direc on. Since the o set is random it can be either way around. The o set voltage is
such an important characteris c that they also list the expected long term dri and
temperature coe cient as well.
This a ects the integra ng ampli er the most. The integrator should produce an output
as we saw in the pre-lab assignment:
t
1
R1C ∫0 IN
VOUT (t) = − V + VOUT (0)
If we account for the input o set:
1
ff tifiti
ff ffff tiffi fftiti 𝜇 fifftifi fiti ff ti tifi ff ft titi
, ESE 272 Laboratory 6
−1 t
R1C 2 ∫0 IN
VOUT (t) = (V + VIO) dt + VOUT (0)
In the case when the input voltage is zero:
−1 t
R1C 2 ∫0 IO
VOUT (t) = V dt + VOUT (0)
The constant VIO can be integrated to yield:
−1
VOUT (t) − VOUT (0) = VIO t
R1C 2
We are going to be integra ng a very small (posi ve or nega ve) constant voltage. This
will cause the output to dri higher or lower (depending on the sign of the o set) un l
the op amp hits the power supply limit. This usually takes just a few seconds, but it is
en rely random and can take more or less me. Some excep onally good examples may
not appear to dri at all.
Passband gain veri ca on:
We will construct a basic inver ng ampli er to verify the passband gain.
1. Construct the circuit at right using a TLC2274A op amp and the resistor values
you calculated in the prelab. Refer to the datasheet for pin connec on
informa on. Rin is added to provide a load to the func on generator.
2. Set both power supply voltages to 5V with a current limit of 50mA (the circuit
needs about 3mA, we limit the current so that any miswires will not damage
the integrated circuit). Enable the supplies.
3. Set the func on generator to provide a 200mVPP sine wave at 1kHz. Enable
the output.
2
ti
ti ti ft fi ti tift ti fi ti ti ti titi ti ff ti
High, low, and bandpass ampli ers
Objec ves:
In this lab we will explore the basics of frequency selec ve ampli ers using opera onal
ampli ers.
Parts required:
• TLC2274A opera onal ampli er
• Resistors
• Capacitors
O set voltage:
Op amps are not perfect. We say that the output is zero when the voltage between the
inver ng and non-inver ng op amp inputs is zero. But, that is not perfectly true. To make
the output zero, there must be a ny voltage between the inver ng and non-inver ng
inputs due to imperfec ons in the matching of the input transistors. This voltage is called
the input o set voltage (VIO) and is a key metric of op amp performance.
The input o set for our TLC2274A op amp is given in the data sheet:
It is typically around 300 V at room temperature, but can be as high as 1.5 mV over the
whole temperature range. They specify the o set voltage magnitude, but not its
direc on. Since the o set is random it can be either way around. The o set voltage is
such an important characteris c that they also list the expected long term dri and
temperature coe cient as well.
This a ects the integra ng ampli er the most. The integrator should produce an output
as we saw in the pre-lab assignment:
t
1
R1C ∫0 IN
VOUT (t) = − V + VOUT (0)
If we account for the input o set:
1
ff tifiti
ff ffff tiffi fftiti 𝜇 fifftifi fiti ff ti tifi ff ft titi
, ESE 272 Laboratory 6
−1 t
R1C 2 ∫0 IN
VOUT (t) = (V + VIO) dt + VOUT (0)
In the case when the input voltage is zero:
−1 t
R1C 2 ∫0 IO
VOUT (t) = V dt + VOUT (0)
The constant VIO can be integrated to yield:
−1
VOUT (t) − VOUT (0) = VIO t
R1C 2
We are going to be integra ng a very small (posi ve or nega ve) constant voltage. This
will cause the output to dri higher or lower (depending on the sign of the o set) un l
the op amp hits the power supply limit. This usually takes just a few seconds, but it is
en rely random and can take more or less me. Some excep onally good examples may
not appear to dri at all.
Passband gain veri ca on:
We will construct a basic inver ng ampli er to verify the passband gain.
1. Construct the circuit at right using a TLC2274A op amp and the resistor values
you calculated in the prelab. Refer to the datasheet for pin connec on
informa on. Rin is added to provide a load to the func on generator.
2. Set both power supply voltages to 5V with a current limit of 50mA (the circuit
needs about 3mA, we limit the current so that any miswires will not damage
the integrated circuit). Enable the supplies.
3. Set the func on generator to provide a 200mVPP sine wave at 1kHz. Enable
the output.
2
ti
ti ti ft fi ti tift ti fi ti ti ti titi ti ff ti
