REV. B

–10–

AD608

Applications

Figure 22 shows the AD608 configured for operation in a digital

system at a 10.7 MHz IF. The filter’s input and output imped-

ance are parallel terminated using 330

Ω resistors and the con-

version gain is 24 dB. The RF port is terminated in 50

Ω; in a

typical application the input would be matched to a SAW filter

using the impedance data shown previously in Table I.

Figure 23 shows the AD608 configured for narrowband FM op-

eration at a 450 kHz or 455 kHz with an external discriminator.

The IF filter has 1500

Ω input and output impedances— the

input is matched via a resistive divider and the output is termi-

nated in 1500

Ω. The discriminator requires 1 V p-p drive from

a 1 k

Ω source impedance, here provided by a gain-of-2.5 Class

A amplifier.

10.7MHz BPF Z = 330

Ω

R2

330

Ω

C5

0.1µF

R1

330

Ω

C2

100pF

C3

100pF

C4

100pF

C1

1µF

VPOS

LIMO

C6

10nF

SUPPLY

2.7V TO 5.5V

POWER-UP

3V CMOS

LIMITER

OUTPUT

VPOS –1V

±200mV

RSSI OUTPUT

+0.2V TO +1.8V

(20mV/dB)

LO INPUT

–16dBm

RF INPUT

–95dBm

TO

–15dBm

BIAS POINT

AT VPOS/2

IF BIAS POINT

DECOUPLING

BPF REVERSE

TERMINATION

OFFSET-CONTROL

LOOP FILTER

BPF

TERMINATION

C7

18nF

16

15

12

11

10

14

13

9

1

2

5

6

7

3

4

8

AD608

VPS1

COM1

RFHI

RFLO

MXOP

LOHI

COM2

VMID

PRUP

LMOP

COM3

RSSI

IFLO

VPS2

FDBK

IFHI

R3

100

Ω

R4

47k

Ω

R6

51.1

Ω

R5

51.1

Ω

Figure 22. Application at 10.7 MHz. The Bandpass Filter

Can Be a Toko Type SK107 or Murata Type SFE10.7

+5V

R1

51.1

Ω

C1 0.1µF

C2

1nF

GND

R2

51.1

Ω

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

AD608

VPS1

COM1

RFHI

RFLO

MXOP

LOHI

COM2

VMID

PRUP

LMOP

COM3

RSSI

IFLO

VPS2

FDBK

IFHI

R3

374

Ω

R4

1.5k

Ω

R6

1k

Ω

LOHI

RFHI

C3

1nF

R7

1130

Ω

F1

C7

0.1µF

C6 0.1µF

C8 0.1µF

C9

0.2µF

R5 200

Ω

C5 0.1µF

R14

8.66k

R15

24.9k

R13

402

R12

1k

CR1

CR2

R8

1k

R9

1k

C10

0.01µF

R11

3.3k

AUDIO

PRUP

RSSI

JUMPER

F1: TOKO HCFM2–455B

F2: MURATA CFY455S

CR1, CR2: 1N60

Q1: 2N3906

F2

R10

3.3k

Ω

R16

47k

Ω

Q1

C11

0.1µF

C4

1nF

Figure 23. Narrowband FM Application at 450 kHz or 455 kHz