Electromagnetic Signal Detector

This is the circuit of electromagnetic field sensor which can sense electromagnetic field from 40Hz to 140Hz. The IC LF351 and associated components forms the pick-up section. 1uH coil L1 is used for sensing the field and the IC1 performs the necessary amplification. If the picked electromagnetic field is in the audio frequency range, it can be heard through the head phone Z1. There is also a meter arrangement for accurate measuring of the signal strength. Transistor Q1 performs additional amplification on the picked signal in order to drive the meter.

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Electromagnetic Signal Detector

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IC LF351 Description

The IC LF351 is a low cost high speed JFET input operational amplifier with an internally trimmed input offset voltage (BI-FET II™ technology). The device requires a low supply current and yet maintains a large gain bandwidth product and a fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents. The LF351 is pin compatible with the standard LM741 and uses the same offset voltage adjustment circuitry. This feature allows designers to immediately upgrade the overall performance of existing LM741 designs.

The IC LF351 may be used in applications such as high speed integrators, fast D/A converters, sample-and-hold circuits and many other circuits requiring low input offset voltage, low input bias current, high input impedance, high slew rate and wide bandwidth.

Features IC LF351

• Internally trimmed offset voltage: 10 mV
• Low input bias current: 50 pA
• Low input noise voltage: 25 nV/
• Low input noise current: 0.01 pA/
• Wide gain bandwidth: 4 MHz
• High slew rate: 13 V/µs
• Low supply current: 1.8 mA
• High input impedance: 1012 Ohm
• Low total harmonic distortion AV=10,: <0.02% RL=10k, VO=20 Vp-p, BW=20 Hz-20 kHz
• Low 1/f noise corner: 50 Hz
• Fast settling time to 0.01%: 2 µs.