Transcript Embedded Systems Analog Electronics

Embedded Systems
Operational Amplifiers
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps
…very high gain dc-coupled differential amplifiers
with single-ended outputs…
24 transistors
11 resistors
1 capacitor
amplifier gains ~ 105-106
NC
offset null
invert
+15V
out
non-invert
offset null
-15V
about $0.60 a piece
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps
+15V
a few millivolts difference between
inputs will cause the output to swing
full range
V+
output ~ K (V+ - V-)
K ~ 106
V-
-15V
1. output swings dramatically and via
feedback, makes difference
between the inputs go to zero
2. inputs draw no current (10-9A)
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps
What does it mean to say the op amp is stable?
V+
Vout= K (V+ - V-)
V-
stable or unstable?
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps
What does it mean to say the op amp is stable?
V+
Vout= K (V+ - V-)
V-
stable or unstable?
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Negative Feedback
feedback - comparing the output of a system to the desired
output in order to make a signed corrective action
CYBERNETICS
negative feedback - connect the output back to the input in such a
way as to cancel some of the input.
Harold S. Black - patent application on negative
feedback in 1928 was “…treated in the same manner as
one for a perpetual motion machine.”
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Stable Inverting Amplifier
assume V+=V-=GND
I1
I1+I2 = 0
I2
note: low input and output impedance, R1+R2
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Stable Non-Inverting Amplifier
assume V+=V-=GND
large input impedance
Zin ~ 108 W
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Unity Gain Follower
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Current-to-Voltage Converter
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Summing Amplifier
weighted sum?
digital to analog converter?
Laboratory for Perceptual Robotics – Department of Computer Science
OpAmps - Bipolar Power Amplifier
Laboratory for Perceptual Robotics – Department of Computer Science