12

www.johanson dielectrics.com

each A & B electrode. The result is a highly vesatile three node capacitive circuit containing two tightly matched, low inductance capacitors in a compact, four-

terminal SMT chip.

Amplifier Input Filter Example

instrumentation amplifier. This reduced component count by 3-to-1 and costs by over 70% vs.

conventional filter components that included 1% film Y-capacitors.

Parameter

10nF

Discrete

10nF, 2 @ 220 pF

Comments

DC offset shift

< 0.1 µV

< 0.1 µV

Referred to input

Common mode rejection

91 dB

92 dB

Source: Analog Devices, “A Designer’s Guide to Instrumentation Amplifiers (2nd Edition)” by Charles Kitchin and Lew Counts

EMI Filtering:

inductance) and tightly matched inductance of these capacitors provides unequaled high frequency Common-Mode

discrete shunt capacitors or series inductive filters. Differential signal loss is determined by the cut off frequency of

the single line-to-ground (Y) capacitor value of an X2Y.

G1

G2

A

B

Signal 1

Signal 2

Ground

Power Bypass / Decoupling

capacitance and reduces their mounted inductance by 80% or 1/5th the mounted inductance of similar sized MLC

capacitors enabling high-performance bypass networks with far fewer components and vias. Low ESL delivers

improved High Frequency performance into the GHz range.

Power

Ground

G1

G2

A

B

GSM RFI Attenuation in Audio & Analog

GSM handsets transmit in the 850 and 1850 MHz bands using a TDMA pulse

rate of 217Hz. These signals cause the GSM buzz heard in a wide range of

audio products from headphones to concert hall PA systems or “silent” signal

errors created in medical, industrial process control, and security applications.

Testing was conducted where an 840MHz GSM handset signal was delivered

to the inputs of three different amplifier test circuit configurations shown below

whose outputs were measured on a HF spectrum analyzer.

1) No input filter, 2 discrete MLC 100nF power bypass caps.

2) 2 discrete MLC 1nF input filter, 2 discrete MLC 100nF power bypass caps.

3) A single X2Y 1nF input filter, a single X2Y 100nF power bypass cap.

X2Y configuration provided a nearly flat response above the ambient and up to

10 dB imrpoved rejection than the conventional MLCC configuration.