Application information

TSH343

12/17

3.2

PSRR and improvement of power supply noise rejection

Figure 28.

Circuit for power supply bypassing

Figure 29 shows how the power supply noise rejection evolves versus frequency depending

on how carefully the power supply decoupling is achieved.

Figure 29.

Power supply noise rejection

Criteria for choosing the ferrite:

●

In DC, the resistance (R) of the ferrite must be as low as possible to keep +5V power

supply on the chip.

●

In AC, along a 30MHz bandwidth (HD spectrum), the equivalent impedance (Z=R+jX)

must be as high as possible to optimize rejection of the noise generated by the power

supply.

50

Ω

+5V

75

Ω

TSH343

T-bias

AGILENT

4395A

S

R

A

L

50

Ω

+5V

75

Ω

TSH343

T-bias

AGILENT

4395A

S

R

A

L

100k

1M

10M

100M

-80

-70

-60

-50

-40

-30

-20

-10

0

L= Ferrite FBMJ4516HM900

CHF=100nF

CLF=10uF

PSRR

L=2uH

CHF=100nF

CLF=10uF

Frequency (Hz)