Schematic Diagrams

Useful schematic and wiring diagrams. ✔ ✔ Enjoy electronic circuits, let your idea comes to hardware

pre amplifier

Variable Attenuator

This is a variable attenuator circuit. This circuit can be used to reduce the power or amplitude of a signal without appreciably distorting its waveform. Here is the circuit : This circuit uses 2N3685 as a voltage variable resistor with an RDS(on) of 800 Ohm. Using 2N3685 JFET, this circuit will provide excellent electronic gain […]

Magnetic-Pickup Phono Preamplifier

This is a simple circuit of magnetic pickup phono preamplifier. A proper loading to a reluctance is provided by this circuit. Here is the circuit: The gain provided by this circuit is approximately 25dB at 1kHz (2.2mV input for 100mV output). Referenced to 10mV input at 1 kHz, the S +N/N ratio is better than […]


High Gain JFET Audio Amplifier

This is a simple high gain JFET audio amplifier circuit. This circuit need very low power but it provides high gain amplifying function. It also called “JFET µ amp”. Here is the circuit : The lower drain current is, the more gain is obtained because µ of a JFET increases as drain current decreases. However it […]

200 MHz Cascade Amplifier

The 200 MHz JFET has same features below: 1. Low crossmodulation 2. Large-signal handling ability 3. No neutralization 4. AGC controlled by biasiing the upper cascade JFET. Here’s the circuit diagram: The Idss of the upper unit must be greater than the lower unit, that’s the only special requirement of the 200 MHz JFET. [Source: […]

FET Op Amp

THE FM3954 monolithic-dual gives us an ideal low-offset and acts as low-drift buffer function for the LM101A op amp. Track over it’s bias current range thus improving common mode rejection is the excellent matching characteristics of the FM3954. Here’s the circuit diagram: [Source: National Semiconductor Application Note]

Op-Amp Application: Inverting Amplifier

The figure below show an operational amplifier circuit. Closed-loop gain given by this circuit is R2/R1 when this ratio is small compared with the amplifier open-loop gain, and it’s called as inverting circuit. The value of input impedance is equal to R1. Bandwidth of this closed-loop is equal to the unity-gain frequency divided by one […]

Op-Amp Application: Non-Inverting Amplifier

This is a high input impedance non-inverting circuit. This circuit provides a closed loop gain equal to (R1+R2)/R1. The close-loop 3 dB bandwidth of this circuit equal to the amplifier unity-gain frequency divided by the closed-loop gain. Here is the circuit : This circuit is different from an inverting circuit. The input impedance of this […]

Op-Amp Application: Unity Gain Buffer

This circuit is an Unity Gain Buffer. This circuit has a highest input impedance of any OP-AMP circuit. This circuit has a less gain error that is equal to common mode rejection or the reciprocal of the amplifier open-loop gain. The multiplication of the open-loop gain and the differential input impedance parallel with common mode […]

Op-Amp Application: Level Shifting Amplifier

Sometimes, in linear equipment design, it’s necessary to take a voltage which is referred to some dc level and generate an amplified output which is referred to ground. Using a differential amplifier similar to that shown in the circuit diagram below (the upper one) is the most straight-forward way of doing this. However, this circuit […]


Single Supply Summing Amplifier for Audio Mixer

The basis of an audio mixer is an inverting summing circuit below. For real audio mixers, a single-supply voltage is seldom used. To increase dynamic range, the designer will often push an op amp up to, and sometimes beyond it’s recommended voltage rails. Noninverting summing circuits are not recommended, but it’s possible to use. The […]

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