Stereo FM/AM Receiver CXA1538

Description Of Stereo FM/AM Receiver CXA1538

The CXA1538M/N/S is high performance one-chip bipolar ICs designed for FM stereo/AM radios. These include an FM/AM front end, FM/AM IF amplifier, FM/AM detection output and FM stereo demodulator output. Pin 4 is the stereo indicator and VCO check pin. Therefore, in stereo mode (when stereo indicator drive Tr Q2 is switched on), pin 4 voltage lowers down, Q1 is cut off and VCO oscillation waveform can not be seen. In AM mode as well, the oscillation waveform can not be seen as VCO turns off. 


Adjust the free run frequency at 76 kHz ±50 Hz. This IC has a built-in auto blend circuit and a MONO switch is not required as a rule. This circuit controls the separation in proportion to the signal level and reduces noise automatically for stereo reception below the mid electric field when the electric field strength reaches lower than about 40 dBμ. When the electric field strength turns below 10 to 15 dBμ, MONO operation is automatically activated. To switch MONO mode on externally, ground pin 3 with 33 Kohm. This IC has a built-in soft muting circuit. As shown in the following I/O characteristics diagram, 23 dB (Typ.) muting is applied and noise level reduced during weak electric field and out of tune instances.

Features Of Stereo FM/AM Receiver CXA1538

• Low current consumption (In FM mode ID=11.0 mA, in AM mode 8.5 mA, VCC=6.0 V)
• Built-in LED drive circuit for tuning
• Built-in LED drive circuit for stereo indicator
• Built-in muting circuit for the FM band
• Few external parts

AUDIO POWER METER circuit WITH LM3915

This VU (volume-unit) meter is capable of monitoring and displaying

power levels present at the speaker terminals of a stereo audio

power amplifier.


The levels are displayed in ten discrete steps. This meter is not

designed to give an accurate display of the power levels.It is

designed to give an approximate visual indication of the audio

power output of each channel. For many situations - disco, parties this

is all which is required: the flashing LED's add atmosphere to the

situation.

LM3915. This is a monolithic Dot/Bar Display Driver IC made by

National Semiconductor. It takes an analog voltage input on pin 5

then drives 10 LED's providing a logarithmic 3dB/step analog display.

When measuring power, a 3dB increase means that the power input

has doubled. As the power doubles, an additional LED will be lit until

the maximum is reached. The display can be bar or moving dot

depending on the connection of pin 9 to the positive supply. The LED

drive current is regulated which eliminates the need for current

limiting resistors.

The supply voltage can be between 3V to 25V.

Mini Audio Spectrum Analyzer LM3915

   

The circuit has been designed to create a spectrum analyzer that will provide an analysis of

a sound to determine at various frequencies, the volume of sounds that make up the overall

sound spectrum.