A preamplifier (preamp) is an electronic amplifier, used to change a weak electrical signal into a strong output signal which is sufficient to be noise-tolerant & for further processing (or) for transmitting to a power amplifier & a loudspeaker. So without using a preamp, the final signal would be distorted or noisy. These are normally used to amplify signals from analog sensors. Thus, the preamp is frequently located close to the analog sensor to decrease the noise & interference effects. There are different types of preamplifiers available in the market where LA 3161 IC is one of those extensively used in amplifiers & tape decks as a stereo preamplifier. This article provides brief information on LA3161 IC, pin configuration, circuit working, and its applications.
What is LA3161 IC?
LA3161 IC is a dual-channel preamplifier integrated circuit that is used most frequently in car stereo applications. This preamp IC has an in-built voltage regulator which helps in enhancing ripple rejection. This IC needs the least number of exterior parts and its noise level is extremely low. This IC has around 100K of high input impedance.
The LA3161 IC includes two low-noise preamplifiers with superior ripple rejection. Its single-in-line package will make mounting simple. When the operating voltage of this IC is 9V, then it can bear voltages up to 18V. The open loop gain of this IC is 78dB.
The pin configuration of LA3161 IC is shown below. This IC includes 8 pins and each pin and its functionality are discussed below.
- Pins 1 & 8 (Input): These are input pins, so the input is given at these two pins.
- Pins 3 & 6 (Output): These are output pins, so the output is taken at these two pins.
- Pin 2 & 7 (NF): These are negative feedback pins.
- Pin 4 (Vcc): It is a power pin where the power supply is given at this pin.
- Pin 5 (GND): It is a ground pin.
Features & Its Specifications:
The features & specifications of LA3161 IC include the following.
- It has On-chip two preamplifiers
- It has good ripple rejection due to the on-chip voltage regulator
- It needs the least number of exterior parts.
- It has less noise.
- This IC includes 8 pins.
- This IC is available in an 8-pin SIP package.
- Its supply voltage ranges from 9V to 18V.
- Its power dissipation is 8mA.
Equivalent and Replacements
The equivalent LA3161 ICs are; LA7954, LA7221, LA4510, LA7016, LA4510, LA7954, LA1140, LA7910, LA3365, LA1150, LA3160, etc. The replacement of LA3161 IC is; LA3160 IC.
Stereo Preamplifier Circuit with LA3161 IC
The stereo preamplifier circuit with LA3161 IC is shown below. The IC used in this circuit like LA3161 IC is a dual-channel pre-amplifier IC that is used for mainly car stereo applications. This chip has a voltage regulator which improves the ripple rejection. This IC has 100K of impedance and a very low noise level. The LA3161 preamp IC is the main control unit within a stereo (or) home theater system. So it switches simply low-level signals to the audio amplifiers from audio & video sources, which improves the output of the preamp adequately to drive the speaker.
The required components to make this stereo preamplifier circuit mainly include; LA3161 IC, 12V Power supply, Resistors; 100 ohms-2, 150 ohms-1, 7.5K – 2, & 100K-2, capacitors; 0.015uf-2, 10uf,-4, 47uf-2 and 1000pf-1. Connect the circuit as per the circuit diagram shown below.
The working of this stereo preamplifier circuit is; the C10 & C11 capacitors in the circuit are used for filtering the noise, the C8 & C9 capacitors are the input coupling capacitors and the C7 capacitor is the power supply filter capacitor that must be located very near to pin-4. The C1 capacitor & R1, and R2 resistors together interpret the left channel’s frequency characteristics. Similarly, the C2 capacitor & R3, and R4 resistors interpret the right channel’s frequency characteristics. Finally, C4 & C5 work as output coupling capacitors.
This stereo preamplifier changes the weak signal into a strong signal, although, it is not the last output stage. After that, for further proceeding, it provides its output to a power amplifier to provide the last output to the speaker. Therefore, it eliminates the input signal’s noise as well as distortion and strengthens the input signal.
A stereo preamplifier circuit with LA3161 IC is used as the primary stage of an instrument amplifier. It can be used within electrode microphones.
Proper care must be taken to get optimum operation of LA3161 IC.
If LA3161 IC is used in the highest rating, then a small difference within conditions can cause the highest rating to be exceeded, so it leads to a breakdown. So use this IC in the range wherever the highest rating is not exceeded.
Short between Pins
If the supply voltage is applied when the space between pins is shorted, a breakdown or deterioration may occur. When installing the IC on the board or applying the supply voltage, make sure that the space between pins is not shorted with solder, etc.
Breakdown of IC
If this IC is placed inversely and operated as well, then this IC gets breakdown (or) deterioration. Before connecting or operating this IC on the board, make sure the marked face of the IC.
The applications of LA3161 IC include the following.
- LA3161 IC is used mainly in car stereo applications.
- These Preamplifiers are very useful in amplifying low-level signals before they are applied to power amplifiers.
- This IC can be used as a stereo tape head preamplifier.
- This IC is used widely in tape recorders & stereo preamp amplifiers.
Please refer to this link for LA3161 IC Datasheet.
Thus, this is an overview of LA3161 IC, pinout, features, specifications, circuit, working, precautions & its applications. From the above information, finally, we can conclude that Preamplifier IC is used to pre-amplify an extremely small signal into some fixed level and further, it can be amplified by a connected power amplifier circuit. Generally, this IC works as a buffer stage between the input small signal source as well as a power amplifier. Here is a question for you, what is an amplifier?