PD

To Internal Bias

Circuitry Control

50 k

Ω

200

1200

2200

100 k

1 M

10 M

100 M

1 G

f − Frequency − Hz

G = 1

THS4130

THS4131

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SLOS318H

– MAY 2000 – REVISED MAY 2011

POWER-DOWN MODE

The power-down mode is used when power saving is required. The power-down terminal (PD) found on the

THS413x is an active low terminal. If it is left as a no-connect terminal, the device always stays on due to an

internal 50 k

+ 1.4 V =

–3.6 V). By the same calculation, the device is off below –3.6 V. It is recommended to pull the terminal

the power-down state, the amplifier goes into a high-impedance state. The amplifier output impedance is typically

greater than 1 M

Ω in the power-down state.

Figure 41. Simplified Power-Down Circuit

Due to the similarity of the standard inverting amplifier configuration, the output impedance appears to be very

connected to the circuit. Therefore, a current path is allowed between the input of the amplifier and the output of

the amplifier. An example of the closed loop output impedance is shown in Figure 42.

Figure 42. Output Impedance (In Power-Down) vs Frequency

Copyright

© 2000–2011, Texas Instruments Incorporated

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