Selasa, 22 Juni 2010
Logarithmic Amplifier
Unusual frequency compensation gives this logarithmic converter a 100 us time constant from 1 mA down to 100 uA, increasing from 200 us to 200 ms from 10 nA to 10 pA. Optional bias current compensation can give 10 pA resolution
from -55 degree C to 100 degree C.
Sabtu, 19 Juni 2010
Two Transistors Sine Wave Oscillator
This oscillator uses two transistors and operates the crystal in the fundamental mode. C1 and C2 should be about 2 700 pF for 1 MHz, 680 pF for 5 MHz, and 330 pF for 10 MHz. 150 pF can be used for up to 20 MHz. The output is a near
perfect sine wave. Try varying C1 and C2 for best waveform. About 2 to 6 Vpp is available.
Pulse Generator (with Transistor)
Seven-V narrow pulse from 2 Hz to 50 kHz are produced by this circuit. C1 through C4 provide frequency ranges in decode steps. R1 and R2 control the charging time of C1 through C4. R2 is a potentiometer used to set the frequency. R8
controls pulse width. Pulse width varies from 7 us to 10 ms. Depending on the frequency, R8 can be deleted if it is not needed.
Highly-stable 60-Hz sine wave Generator
A highly-stable 60-Hz sine wave can be delivered with this circuit, which offers a different and much simpler approach to gaining a stable amplitude. Capacitor coupling the last stage removes any dc component caused by unequal zener
voltages in the clipping circuit that follows the comparator. (Reprinted with permission from Electronics Design, 11/92, p. 62.)
Audio Oscillator
A Wien bridge oscillator produces sine waves with very low distortion level. The Wien bridge oscillator produces zero phase shift at only one frequency (f = 1/2 P RC) which will be the oscillation frequency. Stable oscillation can occur
only if the loop gain remains at unity at the oscillation frequency. The circuit achieves this control by using the positive temperature coefficient of a small lamp to regulate gain (RF/RLAMP) as the oscillator attempts to vary its output.
The oscillator shown here has four frequency bands covering about 15 Hz to 150 kHz. The frequency is continuously variable within each frequency range with ganged 20 k ohm potentiometers. The oscillator draws only about 4.0 mA
from the 9-V batteries. Its output is from 4 to 5 V with a 10 k ohm load and the RF (feedback resistor) is set at about 5% below the point of clipping. As shown, the center arm of the 5 k ohm output potentiometer is the output terminal. To
couple the oscillator to a dc type circuit, a capacitor should be inserted in series with the output lead. (Texas Instruments, Linear and Interface Circuits Applications, Vol 1, 1985, p. 3-15 and 3-16.)
1 Hz Sine wave generator
This circuit produces a 1-Hz sine wave using two op amps. A single-chip dual op amp could be used as well.
DC Tripler Circuit
This dc voltage-trippler circuit based on the 555 can produce a dc output voltage equal to approximately 3X the dc supply voltage.
DC Quadrupler Circuit
This dc voltage-quadrupler circuit based on the 555 can produce a dc output voltage equal to approximately 4X the dc supply voltage.
Second-Order Polynomial Generator
By using a circuit built with a single analog multiplier and five precision resistors, an output voltage (Vo) can be made to create a second-order polynomial. The circuit implements the following quadratic:
Vo = a + bVx + cVx
The input terminals of IC1 are connected to create a positive square term and present the Vx signal to the output with 1-10-V scale factor. Incorporating the voltage-divider network (resistors R3 and R4) in the input signal path provides
additional attenuation adjustment for the coefficient (c) of the square term in the quadratic. Then the passive adder (resistors R1, R2, and R0) is wired to IC1's internal summing circuit to generate the polynomial's other two terms; the
offset term (a) and the linear coefficient (b).
Audio Equalizer Circuit
AUDIO EQUALIZER
PC-Board Connections:
Terminal Connector Finger
AUDIO INPUT_____________5, 8, 14, 21
AUDIO OUTPUT____________4, 7, 13, 20
+9 - 20 v_______________2
ground__________________1, 6, 9, 12, 11, 6, 19, 22
Except as indicated, decimal values of capacitance are in microfarads (uF); others are in picofarads (pF); resistances are in ohms; k = 1,000
This schematic represents one of four sections (channels) on the PC board.
Designed for communications use, this equalizer circuit uses a Mitsubishi M5226P audio equalizer IC to adjust frequency response. It runs from a 9 to 20 V supply. C6 through C16 are polyester film capacitors of +- 5% tolerance. (QST,
5/90, p. 22-24)
Kamis, 03 Juni 2010
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