NJM2760 Ver la hoja de datos (PDF) - Japan Radio Corporation

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NJM2760

Band Pass Filter for Spectrum Analyzer Display

Japan Radio Corporation  

NJM2760

s APPLICATION NOTE

1. Center Frequency Setting for Band Pass Filters

Band pass filters equivalent circuits as follows.

External Circuit

C

C

Internal Circuit

Rb

to Detector

from Input Buffer

Ra

External Circuit

C

Ra

C

Internal Circuit

Rb

to Detector

from Input Buffer

Fig.1-a. BPF1's Equivalent Circuit

Fig.1-b. BPF2-4 's Equivalent Circuit

Center Frequency (fo) can be formulated as follows.

f0

=

2Q

2πCRb

[Hz], Q=2

Table 1. Center frequency setting example

BPF1 (8kHz)

BPF2 (1.2kHz)

BPF3 (300Hz)

BPF4 (80Hz)

Ra

10 kΩ*)

6.8 kΩ

5.6 kΩ

10 kΩ

Rb

169 kΩ*)

113 kΩ*)

96.5 kΩ*)

169 kΩ*)

C

470pF

4.7nF

22nF

47nF

*) As regards the BPF1, the values of Ra and Rb are fixed. Also as regards the BPF2-4, the values of Rb is fixed.

2. Output Gain Setting for RECout.

Output Voltage of RECout is adjustable by external resistor: R2

Voltage Gain (Gv) is defined as follows.

Vout[Vdc]

Vin[Vpeak]

= Gv

=

R2 [kΩ]

100[kΩ]

–5–

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