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Math
Functions: Logarithmic Circuits
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Circuit Takes Square Root of Input Voltage:
11/20/97 EDN-Design Ideas |
Commutating Amp Performs Log Function: 02/16/95
EDN-Design Ideas |
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Log amp uses capacitor charging law: 01/10/2002
EDN - Design Ideas / The novel logarithmic amplifier
in Figure 1 relies on the exponential charging
characteristics of a simple RC circuit. The
expression for the time, T, required for a
capacitor, C, to reach a voltage (VIN-VK) from 0V,
when charged through a resistor, R, with an applied
voltage of VIN, is VIN-VK=VIN (1-e-T/RC), where VK
is a fixed voltage. . |
Logarithmic Amplifier: Logarithmic amplifier
uses the log caracteristic of PN (diode, transistor)
to implement logarithmic function. The second
transistor is used as refference and with the PTK
resistor minimizes the dT/dV coeficient.
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Model Fixed Point DSP Arithmetic in C: 03/18/99
EDN-Design Ideas / PDF contains multiple circuits -
scroll to find this circuit
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Primer on Binary Arithmetic Rounding: 01/21/99
EDN-Design Ideas / PDF contains multiple circuits -
scroll to find this circuit
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Reference stabilizes exponential current:
10/25/2001 EDN - Design Ideas / In an antilog
converter, the difference between the base voltages
of two transistors sets the ratio of their collector
currents: The use of matched transistors balances
the first-order temperature coefficient but leaves a
temperature-dependent gain term, q/kT. Classic
antilog circuits use a thermistor in the drive
circuitry to correct this temperature dependency. . |
Software Filter Boosts Signal Measurement Stability,
Precision: 02/03/03 Electronic Design - Ideas
for Design / Small or embedded systems often require
a delicate measurement in the presence of high noise
or interference. Without fancy filtering hardware,
high-speed processing, or digital signal processing,
it can be difficult to extract a stable signal of...
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Square Root Function Improves Thermostat:
09/30/99 EDN-Design Ideas / Perhaps the most
elementary rule of control-loop design theory is
that feedback-loop performance is fundamentally
linked to the careful choice—and stability—of loop
gain. Insufficient loop gain leads to poor setpoint
accuracy. Too much gain can induce feedback
instabilities, such as overshoot, ringing, and,
ultimately, oscillation. Therefore, the greater the
accuracy you expect from a control system, the more
critical maintaining near-optimal loop gain becomes. |
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