The circuit"s frequency of oscillation is/= 2.8/ [C1 x (R1 + R2)]. Using the values shown, the output frequency can be varied from 60 Hz to 20 kHz by rotating potentiometer R2. A portion of IC1"s output voltage is fed to its noninverting input at pin 3. The voltage serves as a reference for capacitor Cl, which is connected to the noninverting input at pin 2 of the IC. ..
This VCO uses an LF356 op amp to produce a linear frequency vs. voltage characteristic using the CMOS HC4046. The frequency rang..
One section of the precision audio frequency generator uses an electret microphone element to pick up audio from the piano. That signal is then processed and sent to one channel of a dual-trace oscilloscope. The other section of the circuit is used to produce a variable-frequency signal that is fed to a digital frequency counter...
This circuit produces a sinusoidal output of about 8 V pk-pk, which can be varied down to zero, at about 500 Hz. ..
The frequency of this sine-wave oscillator is determined by a direct voltage, U" of 0 to 15 V. The distortion on..
A 555 timer configured as an astable multivibrator is used in this circuit lo generate an audio note...
The following transistors may be used: HEP-254, OC-2, SK-3004, AT30H..
A phototransistor senses daylight. At dusk, it ceases to conduct and Rl biases Q2, activates Kl, and ..
This circuit generates sinusoidal, square, and triangle waveforms simultaneously. Set the frequency to a particular value or vary it, as-shown above. An op amp can be added for extra drive capability and simplified amplitude adjustment. ..
This circuit produces a 20-MHz clock phase locked to a 10-MHz clock present in the Apple MAC II. To generate..
Capacitor CI charges through resistor Rl, and when the gate level established by potentiometer R2 is high enou..
An LM386 audio power IC is set up as a feedback oscillator. Any supply from 6 to 12 V can be used. ..
Field effect transistor, Ql, operates in the linear resistive region to provide automatic gain control. Because the attenuation of the RC network is one-third at the zero phase-shift oscillation frequency, the amplifier gain determined by resistor R2 and equivalent resistor R1 must be just equal to three to make up the unity gain positive feedback requirement needed for stable oscillation. Resistors R3 and R4 are set to approximately 1000 ohm less than the required R1.....
Almost any transistor will work..
Wien bridge oscillator generates frequencies of 1 Hz and 2 to 20 Hz in 2 Hz steps. Maximum output amplitude is 3 volts rms of 8 volts peak-to-peak..
Circuit oscillates because the transistor shifts the phase of the signal 180Â° from the base to the collector. Each of the RC networks in the circuit is designed to shift the phase 60Â° at the frequency of oscillation for a total of 180Â°..
A CD4046 can be gated either with a switch or electronically, as shown in the figure. Frequency range of this circuit ..
A VOX is a voice-operated switch that is often used as a substitute for the press-to-talk switch on" a microphon..
A single transistor makes a simple phase shift oscillator. The output is a sine wave with distortion of about 104. The sine wave purity can be increased by putting a variable resistor (25 ohms) in the emitter lead of Q1 (x). The resistor is adjusted so the circuit is only just oscillating, then the sine wave is relatively pure. Operating frequency may be varied by putting a 10 K variable resistor in series with R3, or by changing CI, C2, and C3..
Varying the amount of this comparator circuit"s hysteresis makes it possible to vary output frequencies in the 740-Hz to 2-kHz range smoothly..
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Low Frequency Amplifiers
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