Transcript Operational Amplifiers and Other Integrated Circuit Usage

Operational Amplifiers
and Other Integrated
Circuit Usage
Jimmie Fouts
Houston County Career Academy
What is the Op-Amp
• One of the most versatile electroinic
circuits!
• Utilizes external feedback to control
response
• Normally operates at high gain, high
input impedance, low output
impedance, and wide bandwidth
• Most common integrated circuit is
the 741 (LM 741, NE 741, µA 741)
History
• The term Op-Amp originated in 1943
by Ragazzinni and Philbrick
• Early Op-Amps were introduced in
1952 and consisted of electron tubes
• Modular, solid state devices
introduced in 1963 by Fairchild
Semiconductors
• The first solid state device was the
µA 702
µA 702 Integrated Circuit
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Manufactured by Fairchild
First solid-state monolithic circuit
Used +12 and – 6 VDC power supplies
Quick to “burn out” if shorted!
Contained only 9 transistors
Cost was $300. in 1963 dollars!
µA 709
• Introduced by Fairchild in 1965
• Higher gain, larger bandwidth, lower
input current than the µA 702
• More user friendly power
requirement of +/- 15 VDC
• High production demands resulted in
initial price of $70 per IC
• By 1969, they were so common that
they were selling for around $2 each
National Semiconductor
• Widlar, the original developer of the
Fairchild ICs, developed the LM 101
in 1967
• The LM 101 was more versatile
– Included short circuit protection
– Frequency compensation
– Later versions included temperature
compensation and offset compensation
Continued Development
• Over time the basic µA 741 has
continued to develop
• Other manufacturers have produced
similar versions
• Raytheon began producing a chip
with quad op-amps in 1974
• National Semiconductors produced
the quad version (LM 324) also
• RCA begin making it with an FET
input for extremely low input current
requirements
Specification Sheets
• Device specification sheet identify
key information about the device
• Most important is the Pin Layout
The IC Pin Layout
• Defines the pin layout of the
integrated circuit
• Most important to troubleshooting a
circuit with an IC
• Eliminates the need for a detailed
schematic of the internal makeup of
the IC
• The chip marking/indent on top
identifies Pin 1
• With Pin 1 in the upper left, pins are
numbered down, then to the left,
then up
Absolute Maximum Parameters
• Supply Voltage
– Maximum safe
+/- input voltage
• Input Voltage
– Maximum signal
input allowed
• Dissipation
– Maximum
allowable power
• Differential Input
– Maximum + and –
input voltage
allowed
Input Parameters
• Input Offset Voltage
• Input Bias Current
– Voltage required for 0
volt output
– Average current flow
through both inputs
• Input Resistance
– Resistance on the input
with other input
grounded
• Input Voltage Range
– Range of commonmode input signals
Output Parameters
• Output Resistance
– Resistance seen at
the output
• Output Voltage
Swing
– Peak output voltage
without clipping
• Output Short Circuit
Current
– Maximum output
current
Dynamic Parameters
• Open Loop Voltage
Gain
– Voltage ratio output to
input
• Slew Rate
– Time rate of change in
output for a gain of 1
• Large Signal Gain
–
Maximum swing to drive
output from 0 to a specified
voltage
Other Parameters
• Supply Current
– Current required from
the power source
• Channel Separation
– Ability to reject
“crosstalk”/other
signals on same chip
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Common Mode Rejection
–
Ability to reject signals
presented at both inputs
simultaneously
• Open Loop Gain
– Output gain vs.
frequency
741 Integrate Circuit Pin Function
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Pin 1 – Used to minimize offset
Pin 2 – Inverted signal to output
Pin 3 – Non-inverted signal to output
Pin 4 - Vcc ´ - Negative power supply input
Pin 7- Positive power supply input
Pin 5 – Used to minimize offset
Pin 6 – Output
Pin 8 – Not Connected
TRANSITIONAL
µA 741
• Fairchild began producing the µA741
in 1968
• Similar to the LM 101 it included
– An on-chip capacitor for frequency
compensation
– Temperature compensation
– Higher speed
– Lower input current
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