LM3900 PDF

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LM LM LM Quad Amplifiers. General Description. The LM series consists of four independent dual input internally compensated amplifiers . Texas Instruments LM Series Operational Amplifiers – Op Amps are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for . lm are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for lm

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With the values shown, this circuit oscillated at Hz, the output swinging from near zero to The unity-gain buffer is a special case of the noninverting amplifier, shown at the right with biasing by means of a voltage divider. They also provide a large output swing.

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It relies on the diode drop at the inverting input to supply a current proportional to V bewhich is then amplified by the feedback resistor. These are the trip levels expressed in currents.

The input and supply voltages can be exchanged to give a noninverting circuit. The relaxation oscillator makes use of a Schmitt trigger, with positive feedback. It has been replaced by a common-mode current lm300 by the current differencing. Multi-channel audio mixer circuit using LM john July 27, 4 Comments. A pass transistor can be added at the output for additional current capacity the LM can be depended on only for about 20 mA when sinking current.

The hysteresis can be displayed directly on the scope, using ln3900 X-Y display. The output goes from high to low when the input reaches 7 V, and from low to high when it goes below 6 V, with a hysteresis of 1 V.


Capacitors C1 to C4 are the decoupling capacitors for the corresponding channels. A relaxation oscillator is shown at the left. The input resistor turns the applied voltage into a current, while the feedback resistor causes the output to rise to a value supplying an equal current to the inverting input.

Om3900 built in amplifier of each section amplifies every audio input separately and is fed to the output terminals.

National Semiconductor – datasheet pdf

Here, the current supplied by the output is returned to the inverting input, where it flows out the k bias resistor, so the bias is positive.

A Hz triangle wave from a function generator makes a suitable input. LM multi-channel audio mixer. However, these op-amps are very different from the usual op-amp, and must be used in a completely different way.

The circuit consists of 4 channel quad amplifier LM Connect Ch 1 to the input voltage, and Ch 2 to the output.

LM3900 Quad Op Amp IC

A voltage regulator with a Zener in the feedback loop is shown at the right. The LM is very convenient for AC amplifiers. An inverting Schmitt trigger is shown at the right. This is a very rough calculation, so we expect only general agreement. Hello, can I use 3. It looks like the same circuit for the usual op-amp, but here the resistors are necessary. The slew rate of the LM was evident in the output waveform. By adding the same circuit parallel with this, you can increase the number of inputs according to the applications.

I think resistors R8 and R10 should be taken out. The usual op-amp responds to a differential voltage at its inputs, but the LM responds to a differential current.


The label “Norton” refers to the Norton equivalent circuit for a current source. It supplies a current 12 – 0. The Norton op-amp can also be used to make active filters and oscillators; see the National Semiconductors application note AN for details.

When the capacitor voltage reaches this level, the ouput again goes high, and the cycle repeats. The output, however, is a voltage as with the usual op-amp.

This is just like the usual op-amp, except with current instead of voltage. Multi channel audio mixer circuit. Km3900 LM is a pin DIP containing four identical op-amps, each with inverting and noninverting inputs and an output. There is one set of power connections for the four amplifiers, but they are otherwise independent. In this case, the bias does not depend on the supply voltage.

Note the symbol for the Norton op-amp, that has a current source between the inputs, and an arrow on the noninverting input. Actual measurement gave 5.

A simple multi-channel audio mixer circuit using LM quad amplifier is given below. The first circuit to look at is the inverting amplifier, shown at the right.

Buffered, this would be an easy way to get a sine wave. This voltage is added to the Zener voltage at the output. Another biasing scheme for the inverting amplifier is shown at the left. Each input is connected to the inverting terminal of LM Two mic audio inputs and two direct line inputs are available in this circuit.