Frequency Translation: The frequency translation means shifting the frequency of an oscillator by a small factor. Fig. 2.134 shows the block schematic for frequency translator using PLL. It consists of mixer, low pass filter and the PLL. The input frequency fs which has to be shifted is applied to the mixer. Another input to the […]

AM Detection: AM Detection – A PLL can be used to demodulate AM signals as shown in the Fig. 2.133. The PLL is locked to the carrier frequency of the incoming AM signal. Once locked the output frequency of VCO is same as the carrier frequency, but it is in unmodulated form. The modulated signal […]

Frequency Shift Keying (FSK) Demodulator: In digital data communication, binary data is transmitted by means of a carrier frequency. It uses two different carrier frequencies for logic 1 and logic 0 states of binary data signal. This type of data transmission is called Frequency Shift Keying (FSK). In this data transmission, on the receiving end, […]

FM Detector Block Diagram: The PLL can be very easily used as an FM detector or demodulator. Fig. 2.131 shows the FM Detector Block Diagram. In the FM Detector Block Diagram, when the PLL is locked in on the FM signal, the VCO frequency follows the instantaneous frequency of the FM signal, and the error […]

PLL Frequency Synthesizer Block Diagram: The PLL can be used as the basis for frequency synthesizer that can produce a precise series of frequencies that are derived from a stable crystal controlled oscillator. The Fig. 2.130 shows the Frequency Synthesizer Block Diagram. It is similar to frequency multiplier circuit except that divided by M network […]

Frequency Multiplier using PLL 565: Fig. 2.128 shows the block diagram for a frequency multiplier using PLL 565. Here , a divide by N network is inserted between the VCO output (pin 4) and the phase comparator input (pin 5). Since the output of the divider is locked to the input frequency fi, the VCO […]

Monolithic Phase Locked Loop IC 565: Monolithic Phase Locked Loop IC 565 are introduced by signetics as SE/NE 560 series and by National semiconductor as LM 560 series. The SE/NE 560 series includes SE/NE 560, 561, 562, 564, 565 and 567. These ICs are differ mainly in operating frequency range, power supply requirements, and frequency […]

Important Definitions Related to PLL: Some important definitions related to PLL are as follows : Lock Range: When PLL is in lock, it can track frequency changes in the incoming signal. The range of frequencies over which the PLL can maintain lock with the incoming signal is called the lock range or tracking range of […]

Phase Locked Loop Working: A Phase Locked Loop Working is basically a closed loop system designed to lock the output frequency and phase to the frequency and phase of an input signal. It is commonly abbreviated as Basics of PLL. The PLL was first introduced in its discrete form in early 1930s. The high cost […]

Foldback Current Limiting: The disadvantage of constant current limit is relatively large power dissipation in the series pass transistor when the load terminals are shorted. Thus a large power rating transistor is required. The Foldback Current Limiting technique allows us to provide the necessary load current at rated voltage but reducing the short circuit current. […]