|Datasheet||Download MC1374 datasheet
The MC1374 includes an FM audio modulator, sound carrier oscillator, RF oscillator, and RF dual input modulator. It is designed to generate a TV signal from audio and video inputs. The MC1374's wide dynamic range and low distortion audio make it particularly well suited for applications such as video tape recorders, video disc players, TV games and subscription decoders. Single Supply, 12 V
Channel or 4 Operation Variable Gain RF Modulator Wide Dynamic Range Low Intermodulation Distortion Positive or Negative Sync Low Audio Distortion Few External ComponentsDevice MC1374P Operating Temperature Range to +70°C Package Plastic DIP
V Channel R6 2.2k Shaded Parts Optional 4 Turns #22, 1/4 Dia. 40 Turns, #36, 3/16 Dia.
Rating Supply Voltage Operating Ambient Temperature Range Storage Temperature Range Junction Temperature Power Dissipation Package Derate above 25°C Value 65 to mW/°C Unit Vdc °C WELECTRICAL CHARACTERISTICS (VCC = 12 Vdc, = 67.25 MHz, Figure 4 circuit, unless otherwise noted.)
Characteristics AM OSCILLATOR/MODULATOR Operating Supply Voltage Supply Current (Figure 1) Video Input Dynamic Range (Sync Amplitude) RF Output (Pin , No External Load) Carrier Suppression Linearity to 12.5% Carrier, 15 kHz to 3.58 MHz) Differential Gain Distortion (IRE Test Signal) Differential Phase Distortion (3.58 MHz IRE Test Signal) 920 kHz Beat (3.58 MHz 30%, 4.5 MHz @ 25%) Video Bandwidth (75 Input Source) Oscillator Frequency Range Internal Resistance across Tank (Pin 6 to Pin 7) Internal Capacitance across Tank (Pin 6 to Pin dB % Degrees dB MHz k pF Min Typ Max Unit
ELECTRICAL CHARACTERISTICS (TA = 25°C, VCC = 12 Vdc, 4.5 MHz, Test circuit of Figure 11, unless otherwise noted.)
Audio Distortion (±25 kHz Deviation, Optimized Bias Pin 14) Audio Distortion (±25 kHz Deviation, Pin 14 self biased) Incidental AM (±25 kHz FM) Audio Input Resistance (Pin 14 to ground) Audio Input Capacitance (Pin 14 to ground) Stray Tuning Capacitance (Pin 3 to ground) Effective Oscillator Source Impedance (Pin 3 to load)
The MC1374 contains an RF oscillator, RF modulator, and a phase shift type FM modulator, arranged to permit good printed circuit layout of a complete TV modulation system. The RF oscillator is similar to the one used in MC1373, and is coupled internally in the same way. Its frequency is controlled by an external tank on Pins 6 and by a crystal circuit, and will operate to approximately 105 MHz. The video modulator is a balanced type as used in the well known MC1496. Modulated sound carrier and composite video information can be put in separately on Pins 1 and 11 to minimize unwanted crosstalk. A single resistor on Pins 12 and 13 is selected to set the modulator gain. The RF output at Pin is a current source which drives a load connected from Pin 9 to VCC. The FM system was designed specifically for the TV intercarrier function. For circuit economy, one phase shift circuit was built into the ship. Still, it will operate from 1.4 MHz to 14 MHz, low enough to be used in a cordless telephone base station (1.76 MHz), and high enough to be used FM IF test signal source (10.7 MHz). At 4.5 MHz, a deviation ± 25 kHz can be achieved with 0.6% distortion (typical). In the circuit above, devices Q1 through Q7 are active in the oscillator function. Differential amplifier Q4, Q5, and Q6 acts as a gain stage, sinking current from input section Q1, Q2 and the phase shift network R17, C1. Input amplifier Q1, Q2 can vary the amount of "in phase" Q4 current to be combined with phase shifter current in load resistor R16. The R16 voltage is applied to emitter follower Q7 which drives an external LC circuit. Feedback from the center of the LC circuit back to the base of Q6 closes the loop. As audio input is applied which would offset the stable oscillatory phase, the frequency changes to counteract. The input to Pin 14 can include a dc feedback current for AFC over a limited range. The modulated FM signal from Pin 3 is coupled to Pin 1 of the RF modulator and is then modulated onto the AM carrier.
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