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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It relies on the diode drop at the inverting input to supply a current proportional to V bewhich lk3900 then amplified by the feedback resistor. The input and feedback resistors are as with the familiar circuit, and the gain in this case should be Previous post Next post.

The capacitor charges until its voltage reaches this level, but then the ouput goes low and lm300 begins to discharge again. Another biasing scheme for the inverting amplifier is shown at the left. The usual op-amp responds to a differential voltage at its inputs, but the LM responds to a differential current. The divider ml3900 a current into what is effectively a unity-gain buffer to reproduce its voltage at the output. However, these op-amps are very different from the usual op-amp, and must be used in a completely different way.

Two mic audio inputs and two direct line inputs are available in this circuit.

Muti-channel audio mixer circuit based on LM IC. Four channels.

The relaxation oscillator makes use of a Schmitt trigger, with positive feedback. There is one set of power connections for the four amplifiers, but they are otherwise independent. Equal currents supplied to the two inputs are not amplified.

Again, the high input impedance of the voltage op-amp is not obtained. The difference is the 39k resistor at the noninverting input. In this case, the bias does not depend on the supply voltage.

Another difference that is immediately obvious is that the inputs are one diode drop, about 0. Capacitors C1 to C4 are the decoupling capacitors for the corresponding channels.


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. LM series amplifiers consist of four independent and internally compensated amplifiers that are designed for single and wide power 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. The input and supply voltages can be exchanged to give a noninverting circuit.

LM3900 Quad Op Amp IC

Multi-channel audio mixer circuit using LM john July 27, 4 Comments. It looks like the same circuit for the usual op-amp, but here the resistors are necessary.

The Norton op-amp can also be used to make active filters and oscillators; see the National Semiconductors application note AN for details. The circuit is not as precise as the usual one, with small shifts due to the diode drops at the input, but the circuit is useful and furnishes a reasonable input resistance of 1M.

The circuit consists of 4 channel quad amplifier LM 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. When you test this circuit, the scope traces for input and output can be superimposed with proper setting of the gain, and the inversion is obvious.

Its output swings from very near ground to a diode drop below the positive supply.

By adding the llm3900 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. This is an AC amplifier, with coupling capacitors at input and output so there is no worry about DC bias levels, which can be chosen as necessary. Actual measurement gave 5.

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The label “Norton” refers to the Norton equivalent circuit for a current source. The LM can use from 4 to pm3900 V total supply voltage.


The extremely llm3900 input resistance of the voltage or FET-input op-amp is not obtained, however. 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.

A ln3900 buffer is shown at the left. LM pin configuration and architecture. This voltage is added to the Zener voltage at the output. LM multi-channel audio mixer. The LM is specially useful when only a single power supply is available.

The output, however, is a voltage as with the usual op-amp. The unity-gain buffer is a special case of the noninverting amplifier, shown at the right with biasing by means of a voltage divider.

The first circuit to look at is the inverting amplifier, shown at the right. An inverting Schmitt trigger is shown at the right. To understand this circuit, assume for simplicity that the output swings from 0 to the supply voltage V. The LM is very convenient for AC amplifiers. When the capacitor voltage reaches this level, the ouput again goes high, and the cycle repeats.

Each input is connected to the inverting terminal of LM It has been replaced by a common-mode current range by the lm3900 differencing.

The measured values from the scope were 3. The LM is a lm3090 DIP containing four identical op-amps, each with inverting and noninverting inputs and an output. The hysteresis can be displayed directly on the scope, using the X-Y display. Calvert Created 10 August Last revised 19 September The slew rate of the LM was evident in the output waveform.

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.