LTC6242IGN datasheet(19/24 Pages) LINER

19 / 24 page

LTC6241/LTC6242

62412f

APPLICATIO S I FOR ATIO

Low Noise Shock Sensor Ampliﬁers

Figures 9 and 10 show the LTC6241 realizing two different

approaches to amplifying signals from a capacitive sensor.

The sensor in both cases is a 770pF piezoelectric shock

sensor accelerometer, which generates charge under

physical acceleration.

Figure 9 shows the classical “charge ampliﬁer” approach.

The LTC6241 is in the inverting conﬁguration so the sensor

looks into a virtual ground. All of the charge generated

by the sensor is forced across the feedback capacitor

by the op amp action. Because the feedback capacitor

is 100 times smaller than the sensor, it will be forced to

100 times what would have been the sensor’s open circuit

voltage. So the circuit gain is 100. The beneﬁt of this ap-

proach is that the signal gain of the circuit is independent

of any cable capacitance introduced between the sensor

and the ampliﬁer. Hence this circuit is favored for remote

BIAS RESISTOR

VISHAY-TECHNO

CRHV2512AF1007G

(OR EQUIVALENT)

MAIN

GAIN-SETTING

ELEMENT IS A

CAPACITOR

SHOCK SENSOR

MURATA-ERIE

PKGS-00LD

770pF

CABLE HAS

UNKNOWN C

6241 F09

VOUT = 110mV/g

–

1/2

LTC6241

7.7pF

Figure 9. Classical Inverting Charge Ampliﬁer

accelerometers where the cable length may vary. Difﬁculties

with the circuit are inaccuracy of the gain setting with the

small capacitor, and low frequency cutoff due to the bias

resistor working into the small feedback capacitor.

Figure 10 shows a non-inverting ampliﬁer approach. This

approach has many advantages. First of all, the gain is set

accurately with resistors rather than with a small capaci-

tor. Second, the low frequency cutoff is dictated by the

bias resistor working into the large 770pF sensor, rather

than into a small feedback capacitor, for lower frequency

response. Third, the non-inverting topology can be paral-

leled and summed (as shown) for scalable reductions in

voltage noise. The only drawback to this circuit is that the

parasitic capacitance at the input reduces the gain slightly.

This circuit is favored in cases where parasitic input

capacitances such as traces and cables will be relatively

small and invariant.

BIAS RESISTOR

VISHAY-TECHNO

CRHV2512AF1007G

(OR EQUIVALENT)

6241 F10

10k

100

Ω

VOUT = 110mV/g

VS = ±1.4V to ±5.5V

BW = 0.2Hz to 10kHz

VOUT

–

1/2

LTC6241HV

–

10k

100

Ω

–

1/2

LTC6241HV

SHOCK SENSOR

MURATA-ERIE

PKGS-00LD

770pF

Figure 10. Low Noise Non-Inverting Shock Sensor Ampliﬁer

LTC6242IGN 数据表(PDF) 19 Page - Linear Technology

LTC6242IGN 数据表(HTML) 19 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

数据表下载