OP183

Rev. D | Page 15 of 16

LOW VOLTAGE FREQUENCY SYNTHESIZER FOR

WIRELESS TRANSCEIVER

The low noise and low voltage operation capability of the

OP183 serves well for the loop filter of a frequency synthesizer.

Figure 39 shows a typical application in a radio transceiver. The

phase noise performance of the synthesizer depends on low

noise contribution from each component in the loop as the

noise is amplified by the frequency division factor of the

prescaler.

The resistors used in the low-pass filter should be of low to

moderate values to reduce noise contribution due to the input

bias current as well as the resistors themselves. The filter cutoff

frequency should be chosen to optimize the loop constant.

3V

OP183

PHASE

DETECTOR

REFERENCE

OSCILLATOR

CRYSTAL

÷

PRESCALER

RF

OUT

VCO

900MHz

Figure 39. Low Voltage Frequency Synthesizer for a Wireless Transceiver

7

6

4

1

3

5

2

BA

QB3

QB1

QB2

RB2

RB1

QB4

QB5A

CB1

R10

R3LT

R3AT

R3A

R3B

CC1

R4A

R4B

R11

R4LT

R4AT

QB12

QB13

Q1

Q2

Z1

R1

R2

JB1

QB9

QB10

QB6

RB3

RB4

RB5

RB6

QB7

Q7

Q8

QB8

Q5

QD1

Q6

Q3

Q4

CF1

R5

CC3

QB11

QD2

R9

Q12

CC2

R8

QD3

CO

R7

Q11

Q10

QB14

Figure 40. OP183 Simplified Schematic