Conex Club Magazine - no.2 - 2002

Conex Club Magazine - no.2 - 2002 - LM833 low noise amplifier

Reading time: 2 minute

The main topics presented

1. AD606 (50 MHz, 80 dB Demodulating Logarithmic with Limiter Output)

The AD606 circuit is a monolithic logarithmic demodulator with a dynamic of 80dB. It is powered by 5V and consumes 65mW.

It is used in various types of receivers, especially in mobile telephony and many other FM transmission applications.

2. SIM card (elements for study and applications)

SIM cards very well known to the general public are those intended especially for prepaid services such as: Fixed or cellular public telephony; Public laundry services; Urban car park services and others.

But the possibilities offered by the banal card are little exploited. That is why the knowledge strictly necessary for understanding the way of functioning or for the development of various applications is recapitulated in a didactic way.

3. Function generator

There is a signal generator: sinusoidal, triangular, ramp and rectangular. The integrated circuit that makes the three basic waveforms (sinusoidal, triangular and ramp) is of the type XR2206CP.

The rectangular waveform is taken from the sync output of the circuit and therefore it can only be attenuated.

Technical data:

  • Frequency: 0 - 200kHz;
  • Game frequency: 6;
  • Fine frequency adjustment within each range;
  • Functions: 4 (Sinusoidal, Triangular, Ramp, Rectangular);
  • Attenuation: 4 steps (0dB, 20dB, 40dB, 60dB);
  • Amplitude: continuously adjustable within an attenuation stage for the first three waveforms;
  • DC axis: -75%, + 75% of the double supply voltage;
  • Outputs: 3 {600 Ohm and 50 Ohm with DC axis; AC (approx. 1.5 Ohm) (without DC component)} (impedance that can be connected to the AC output is> / = 600 Ohm);
  • Sweep input (of the frequency within the chosen range.): 3.2V / min. / 50 Ohm;
  • Power supply: double source +/- 9V (batteries), +/- 12V;
  • Consumption: 50mA, 60mA.

4. Printed circuits - Evaluation of a special discontinuity

Printed circuits inevitably have a wide range of discontinuities. In 2001, during two articles, the discontinuity "corner" was presented in the pages of Conex Club magazine.

It is specified then that this is not the most dangerous, and that others, at first sight non-existent or at most banal, prove to be much harsher elements in the way of a quality transmission of useful signals from the generator circuit to the circuit / circuits receivers.

The discontinuity that will be the subject of this article is the branch of the route, called in English "branch".

5. LM833 low noise amplifier

For a long time, the LM381 amplifier (also made in our country by Baneasa SA under the name BM381) was one of the dual low noise operational amplifiers, accessible in price and with good performance for radio frequency applications.

The same company that made LM381 (National Semiconductor) then manufactured another integrated circuit with better performance, LM833, available in our specialty stores. The LM833 amplifier is also dual, but in an 8-pin capsule.

6. Experiments with feeders

The experimental study of physical phenomena on long lines (fiders) requires expensive equipment and highly qualified operators.

The special circuit analysis programs with which these experiments can be simulated on a computer are of general use, so they are expensive and difficult to manipulate.

Starting from the conception that the experiment is the most efficient way of understanding the phenomena, it is presented to the readers. some practical simulation examples using an easy-to-use and easy-to-use program.

7. Matrix display

The article presents an interesting application of the well-known microcontroller PIC16F84 </strong> Microcontroller. from Microchip, namely an animated matrix display of 8 × 8 dots with LEDs.


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