NEC70001AB Audio Amplifier 20W

The 20-W + 20-W stereo amp consists of two complete, separate 20-W RMS bridge-type amplifiers. The input signal source is brought into the amplifier through the voltage divider network, which is made up of Rl, R2, and PI. Resistor Rl provides a load impedance between the signal source and ground. Resistor R2 couples that signal to potentiometer PI.The signal is coupled by capacitor CI to the noninverting (+) input (pin 1) of internal amplifier (A) of IC1, where the signal is greatly amplified. Capacitor C2 couples the (+) input of the other (B) internal amplifier of IC1 to ground. That causes the input signal, which is referenced to ground, to be coupled to both amplifiers because both the inputs and outputs of IC1 (A) and IC1 (B) are connected in a bridge configuration. Notice that the output of IC1 (A) from pin 10 is connected to one side of the speaker and the output of IC1 (B) from pin 8 is connected to the other side of the speaker.That is why the speakers used cannot have one side connected to ground. Resistors R6 and R7 set the gain of the amplifier. Resistors R9 and R10 and capacitors C9 and C10 provide frequency stability and prevent oscillation. Capacitors C6 and C7 provide bootstrapping, which prevents distortion at low frequencies. LED LI lights up by way of a series resistor connected from the anode to +12 Vdc when power is applied.Power for both IC1 and IC2 is brought in through D1 (to protect amplifiers from reverse polarity). Capacitor Cll provides additional power supply line filtering. This booster is capable of producing 20 W RMS output out of each channel. 

NE5118 Programable amplifier

The intention of the following application shows how the NE5517 works in connection with a DAC. In the application, the NE5118 is used—an 8-bit DAC with current output—its input register making this device fully µ-compatible. The circuit consists of three functional blocks. Tthe NE5118 which generates a control current equivalent to the applied data byte, a current mirror, and the NE5517.

L144 Instrumentation amplifier

Three-amplifier circuit consumes only 135 /tW of power from a ±1 V power supply. With a gain of 101, the instrumentation amplifier is ideal in sensor interface and biomedical preamplifier applications. The first stage provides all of the gain while the second stage is used to. provide common mode rejection and double-ended to single-ended conversion.

LM368 Audio Amplifier

This circuit is for low voltage applications requiring high power outputs. Output power levels of LO W into 4 ohm from 6 V and 3 V into 8 ohm from 12 V are typical. Coupling capacitors are not necessary since the output dc levels will-be within a few tenths of a volt of each other Where critical matching is required the 500 K potentiometer is added and adjusted for zero dc current flow through the load.

CA3140 Audio Amplifier

A CA3140 drives a complementary output stage Ql, Q2, and Q3. Output power depends on supply voltage and limits on dissipations of Q2 and Q3, but it can be 1 or 2 W with a higher impedance speaker and a 30-V supply. 

HA-510X Auto-zeroing-scale

Electronic scales have come into wide use and the HA-510X, as a very low noise device, can improve such designs. This circuit uses a staingauge sensing element as part of a resistive Wienbridge. An auto-zero circuit is also incorporated into this design by including a sample-and-hold network. The bridge signal drives the inverting input of a differentially configured HA-5102. The noninverting input is driven by the other half of the HA-5102 used as a buffer for the holding capacitor, CH.

This second amplifier and its capacitor CH form the sampling circuit used for automatic output zeroing. The 20-KO resistor between the holding capacitor CHand the input terminal, reduces the drain from the bias currents. A second resistor RG is used in the feedback loop to balance the effect of R8. If R7 is approximately equal to the resistance of the strain gauge, the input signal from the bridge can be roughly nulled with R6. With very close matching of the ratio R4/Rl i:o R3/R2, the output offset can be nulled by closing Sl. This will charge CH and provide a 0-V difference to the inputs of the second amplifier, which results in a 0-V output. In this manner, the output of the strain gauge can be indirectly zeroed. RIO and potentiometer Rll provide an additional mechanism for fine tuning VouT. but they can also increase offset voltage away from the zero point. Cl and C2 reduce the circuit`s susceptibility to noise and transients.

Auto gain control op-amp circuit

An audio signal applied to VI is passed through the operational amplifier 741, U2. After being amplified, the output signal V2 is sampled and applied to a negative voltage doubler / rectifier circuit composed of diodes CRI and CR2, with the capacitor C1. The resulting negative voltage is used as a control voltage which is applied to the door] 2N5485 FET Q1. Capacitor C2 and resistor R2 form a filter for smoothing the voltage rectified audio control. The lFET is connected between pin 2 of the MC3340P grounded by a resistor of 1 kohm.. As the voltage applied to the gate of FET] becomes more negative in magnitude, the channel resistance of FET] increases causing lFET to function as a voltage-controlled resistor. The MC3340P audio attenuator is the heart of the MCO. It is capable of 13 dB of gain or almost - 80 dB of attenuation as a function of external resistor placed between Pin 2 and ground. An increase in resistance decreases the gain from the MC3340P. The gain of the circuit is not entirely a linear function of the external resistance, but such behavior is similar across much of the gain / attenuation range. An input signal applied to the input of the AGC will cause the gate volt age the proportion lFET become negative. Accordingly, the JFET increases the resistance of the pin 2 to ground the MC3340P causing a reduction in gain. In this way, the AGC output is kept almost constant.