AC-DC & DC-DC Circuits

High Voltage Power Supply for Valve Preamplifiers

The amplifier feeding to the final amplification stage is performed with unstabilized voltage. The output stage, due to push-pull operation, has a large rejection of the supply voltage. The various other steps, however, do not have the same rejection and introduce unwanted noise. So the pre-amplification stage is good to be powered with a... .
Lab Variable Symmetric Power Supply circuit 2x30V 3.5A

The power supply circuitry consists of a 220/2 * 18V / 3.5A transformer, a rectifier, a smoothing filter, a power amplifier, LM301, and two regulators LM317 and LM337. The theoretical of the circuit is shown in the figure. The voltage from the transformer is rectified by the rectifying bridge. Parallel to the bridge diodes, C1, C2, C3, C4, have... .
0-30V Lab Variable Power Supply

At the left side (input AC) goes the secondary of a 220 volt (primary) 18 Volt (secondary) / 3 Ampere mains transformer. The alternating voltage of 18 volts from its secondary transformer is rectified by the diodes D1, D2, D3 and D4, which are connected to a bridge arrangement and make a double rectifier. The pulse from the bridge exit is... .
Anti-RF filtered power supply 12-14 Volt / 3A

This power supply is dedicated for use with rf equipments like, linear amplifiers, transmitters, receivers, and in every application that clean an-noisy signal is required. The circuit is very simple and you can drive it with a 220V/18V/3A transformer at the pins 1and 2.
AC bridge using LF356

The circuit provides a simple and cost-effective solution to matching resistors and capacitors. Impedances ZR and Zx form a half-bridge, while OSC and OSC excite the bridge differentially. The external op amp is a FET input amplifier (LF356) with very low input bias current on the order of 30 pA (typical). CI allows ac coupling by blocking the... .
Bridge circuit

The transistor is connected as an audio oscillator, using an audio transformer in the collector. The secondary goes to a linear pot. .
Over-voltage protection circuit

A silicon-controlled rectifier is installed in parallel with the 12-V line and connected to a normally-closed 12-V relay, K1. The SCR's gate circuit is used to sample the applied voltage. As long as the applied voltage stays below a given value, SCR1 remains off and Kl's contacts remain closed, thereby supplying power to the load. When the... .
400-Volt 60-watt push-pull power supply

The design delivers a regulated 400-V, 60-W output. The TL494 switching regulator governs the operating frequency and regulates output voltage. Rl and Cl determine switching frequency, which is approximately 0.SRCâ€”100 kHz for the values shown. The TL494 directly drives the FET's gates with a voltage-controlled, pulse-width-modulated signal.... .
Power supply monitor

This circuit uses a tricolor LED display to indicate acceptable and unacceptable output voltages. One to set the upper voltage limit, the other, the lower voltage limit. When the monitored voltage is above the set maximum, the LED display turns red. Yellow turns On for voltages below the set minimum, and green turns on for voltages between the... .
Microprocessor power supply watchdog

The circuit monitors the input to the microprocessor 5 V regulated supply for voltage drops and initiates a reset sequence before supply regulation is lost. In operation, the resistor capacitor combination Rs and Cj form a short time constant smoothing network for the output of the fullwave bridge rectifier. An approximately triangular, voltage... .
Bipolar power supply for battery instruments

To generate regulated Â± 5-V supplies from a pair of dry batteries, the circuit of Fig. 1 is commonly used. In order to give protection from inadvertent reverse connection of a battery, a diode in series with each battery would produce an unacceptable voltage drop. The more effective approach is to fit diodes Dl and D2 as shown in Fig. 2, in... .
Low Power consumption 5V regulator circuit

The special feature of the circuit shown below is the low consumption. With voltage n 9 at the entrance and no exit load, absorbs current 50 ma, which is certainly very small compared with a quiescent current 78L05. The components that comprise it are scarce. Just a reference voltage source, formed by the T1 and the IC 1 and an amplifier... .
Bridge balance indicator

Indicator provides an accurate comparison of two voltages by indicating their degree of balance (or imbalance). Detecting small variations near the null point is difficult with the basic Wheatstone bridge alone. Amplification of voltage differences near the null point will improve circuit accuracy and ease of use. The 1N914 diodes in the... .
8-Amp regulated power supply

This supply is powered by a transformer operating from 120 Vac on the primary and providing approximately 20 Vac on the primary, and providing approximately 20 Vac on the secondary. Four 10-A diodes with a 100 PIV rating are used in a full-wave bridge rectifier. A 10,000 ^F/36 Vdc capacitor completes the filtering, providing 28 Vdc. The dc... .
linear regulator

Intended for extreme temperature, radiation-hardened environments, this linear supply is capable of supplying 28 Vdc at 125 A from an ac-driven power unit. In operation, power supply output voltage is sensed by the voltage divider consisting of R24 to R28 and fed to one input of a discrete differential amplifier composed of Q13 through Q16. The... .
Variable current source 100ma-2amp

The output current is set by the resistor R in the collector of Tr2, which may be varied to offer a range of output currents from 100 mA to 2 A with fine control by means of VR3 which varies the reference voltage to the non-inverting input of the op amp. .
Bench top power supply

A tapped transformer drives a diode bridge (D1-D4) and two 2500 ÂµÂ¥ filter capacitors (Cl and C2), that provide a no-load voltage of 37 or 47 volts, depending upon the position of switch S2a. The unregulated dc is then fed to a pre-regulator stage composed of Ql and D5. Those components protect IC1 (the 723) from an over-voltage condition; the... .
Stand-by power for non-volatile cmos rams

To prevent loss of data when a CMOS RAM is switched from normal operation (Vcc = 5 volts) to stand-by mode (Vcc = VBAT) it must be ensured that the CS pin goes near the Vcc rail at all times. Ac coupling to the chip select is made through capacitor C, breaking the dc current path between Vqq (and hence VBAT) and the decoder output. .
Power supply protection circuit

When using a regulated supply to reduce a supply voltage there is always the danger of component failure in the supply and consequent damage to the equipment. A fuse will protect when excess current is drawn, but might be too slow to cope with overvoltage conditions. The values shown are for a 12 V supply being dropped to 5 V. The trip voltage... .
Half-wave rectifier

This circuit provides for accurate half wave rectification of the incoming signal. For positive signals, the gain is 0; for negative signals, the gain is â€” 1. By reversing both diodes, the polarity can be inverted. This circuit provides an accurate output, but the output impedance differs for the two input polarities and buffering may be needed .
Precision full wave rectifier

The circuit provides accurate full wave rectification. The output impedance is low for both input polarities, and the errors are small at all signal levels. Note that the output will not sink heavy current, except a small amount through the 10K resistors. Therefore, the load applied should be referenced to ground or a negative voltage. Reversal... .
Positive input-negative output charge pump

A simple means of generating a low-power voltage supply of opposite polarity from the main supply. Self oscillating driver produces pulses at a repetition frequency of 100 kHz. When the VMOS device is off, capacitor C is charged to the positive supply. When the VMOS transistor switches on, C delivers a negative voltage through the series diode... .
Shift register driver

A16 V power supply can be synthesized as shown using IN1692 rectifiers. A shift pulse input saturates the 2N2714 depriving the Darlington combination (2N2714 and 2N2868) of base drive .
Single transistor phase shifter

This circuit provides a simple means of obtaining phase shifts between zero and 170Â°. The transistor operates as a phase splitter, the output at point A being 180Â° out of phase with the input. Point B is in phase with the input phase. Adjusting Rl provides the sum of various proportions of these and hence a continuously variable phase shift is... .
0 to 360 phase shifter

Each stage provides 0° to 180° phase shift. By ganging the two stages, 0° to 360° phase shift is achieved This circuit is under:, power supplies, ac dc dc dc, 0° To 360° phase shifter l12884. By ganging the two stages, 0° to 360° phase shift is achieved The 2N3070 JFETs do not load the phase shift networks. .
5V 0.5A power supply

The circuit is essentially a constant source modified by the feedback components R2 and R3 to give a constant voltage output. The output of the ZN424E need only be 2 volts above the negative rail, by placing the load in the collector of the output transistor Tr2. The current circuit is achieved by Trl and R5 .
Travellers shaver adapter

Many countries have 115 volts mains supplies. This can be a problem if your electric shaver is designed for 220/240 volts only. This simple rectifier voltage doubler enables motor driven 240 volt shavers to be operated at full speed from a 115 volt supply. As the output voltage is dc, the circuit can only be used to drive small ac/dc motors .
Dual polarity power supply

This simple circuit gives a positive and negative supply from a single transformer winding and one full-wave bridge. Two zener diodes in series provide the voltage division and their centerpoint is grounded .
Mobile voltage regulator

This simple mobile voltage regulator circuit may save your two meter or CB transceiver if the voltage regulator fails. The 2N3055 should be heat sinked if current drawn by the rig is in excess of 2 A on transmit .
Low ripple power supply

This circuit may be used where a high current is required with a low ripple voltage (such as in a high powered class AB amplifier when high quality reproduction is necessary), Ql, Q2, and R2 may be regarded as a power darlington transistor. ZDl and Rl provide a reference voltage at the base of Ql. ZDl should be chosen thus: ZDl = Von-1 .
Low voltage regulators

These short-circuit protected regulators give 6, 7, and 9 V from an automobile battery supply of 13 V nominal; however, they will function just as well if connected to a smoothed dc output from a transformer/rectifier circuit. Two types are shown for both positive and negative ground systems. The power transistors can be mounted on the heatsink... .
Rf probe for vtvm

This circuit combines a 555 timer with a 2N2222 transistor and an external potentiometer. The pot adjusts the output voltage to the desired value. To regulate the output voltage, the 2N2222 varies the control voltage of the 555 IC, increasing or decreasing the pulse repetition rate. A 1 K resistor is used as a collector load. The transistor base... .

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