THS4541 datasheet(46/64 Pages) TI1

46 / 64 page

Frequency (Hz)

-32

-29

-26

-23

-20

-17

-14

-11

10M

100M

D064

Bench without caps

Bench with caps

Sim without caps

Sim with caps

Rf1

402

Rg1

4.02 k

Rg2

4.02 k

THS4541 Wideband,

Fully-Differential Amplifier

Rf2

402

Gain of 0.1 V/V from Rg1,

Single-Ended to Differential,

DC-Coupled, Single Supply

500

Vcc

Vcm

Vcc

5 V

Vcm

2.5 V

VM1

VG1

1 pF

1.7 pF

Vcc

Vocm

Vcc

FDA

THS4541-Q1

SLOS930B – NOVEMBER 2015 – REVISED NOVEMBER 2019

www.ti.com

Product Folder Links: THS4541-Q1

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Typical Applications (continued)

Figure 78. Compensated Attenuator Circuit Using the THS4541-Q1

The 1 pF across the inputs is really a total 1.85 pF, including the internal differential capacitance, and a Cs =

3.7 pF for a single-ended design from Equation 17.

These two designs (with and without the capacitors) were both bench tested and simulated using the THS4541

TINA model giving the results of Figure 79.

This method does a good job of flattening the response for what starts out as a low phase-margin attenuator

application. The simulation model does a very good job of predicting the peaking and showing the same

improvement with the external capacitors; both giving a flat, approximately 250-MHz, closed-loop bandwidth for

this gain of a 0.1-V/V design. In this example, the output noise begins to peak up (as a result of the noise-gain

shaping of the capacitors) above 70 MHz. Use postfiltering to minimize any increase in the integrated noise using

this technique. Using this solution to deliver an 8-VPP differential output to a successive approximation register

(SAR) ADC (using the 2.5-V Vocm shown), the circuit accepts up to ±40-V inputs, where the 4-kΩ input Rg1

draws ±10 mA from the source.

10.2.1.3 Application Curve

Figure 79. Attenuator Response Shapes with and without External Compensation

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