amplificador operacional

LM 741 .- Amplificador Operacional


National



Semiconductor


LM741/LM741A/LM741C/LM741E Operational Ampiifier


General Description


The LM741 series are general purpose operational amplifi-


ers which feature improved performance over industry stan-


dards like the LM709. They are direct, plug-in replacements


for the 709C, LM201, MC1439 and 748 in most applications.


The amplifiers offer many features which make their appli-


cation nearly foolproof: overload protection on the input and
 
output, no latch-up when the common mode range is ex-



ceeded, as well as freedom from oscillations.


The LM741C/LM741E are identical to the LM741/LM741A


except that the LM741C/LM741E have their performance


guaranteed over a 0°C to f 70°C temperature range, in-


stead of - 55°C to ! 125°C
 
download  datasheet LM 741 .- Amplificador Operacional National Semiconductor

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Two Transistors Wireless Microphone FM Transmitter Circuit Schematic Diagram

Two Transistors Wireless Microphone FM Transmitter Circuit Schematic Diagram

Please be warned if operating this circuit might violate the regulation of your country, because this FM transmitter circuit radiate strong radio frequency to the environment. This wireless microphone is very sensitive, pick up every sound in the 20m radius, and transmit the radio signal up to 2 kilometers in open air. Here is the schematic diagram of the circuit:

The first transistor (Q1) is the pre-amplifier for the microphone, and you can ommit this circuit if you don’t want to transmit the sound picked up by the mic, for example you can can connect your mp3 player directly to C1. The core of this FM transmitter circuit is Q2, a modified Collpits oscillator that the frequency is determined by L1, C4, C6, and the transistor’s internal base-emitter capacitance. The antenna use 1/16 wave length to compromize between the efficiency and the size. If you want the microphone to be less sensitive, you can replace the R1 by a higher resistor, try 10k or 22k, and this might overcome the feedback problem if you use this wireless microphone FM transmitter for a public address system.

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