THS4601

SLOS388B – OCTOBER 2001 – REVISED JUNE 2002

20

www.ti.com

APPLICATION INFORMATION

overdrive recovery (continued)

Figure 36

–3

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–4

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Time –

µs

RISING EDGE OVERDRIVE RECOVERY

Gain = 5,

VIN = 5.57 VPP,

Recovery Time = 340 ns

Input

Output

Figure 37

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2

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Time –

µs

FALLING EDGE OVERDRIVE RECOVERY

Gain = 5,

VIN = 5.57 VPP,

Recovery Time = 320 ns

Input

Output

Figure 38

–3

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–10

–5

0

5

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20

01

2

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–4

–2

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Time –

µs

FALLING EDGE OVERDRIVE RECOVERY

Gain = 5,

VIN = 6 VPP,

Recovery Time = 540 ns

Input

Output

Figure 39

–3

–20

–15

–10

–5

0

5

10

15

20

01

23

4

–4

–2

–1

0

1

2

3

4

Time –

µs

RISING EDGE OVERDRIVE RECOVERY

Gain = 5,

VIN = 6 VPP,

Recovery Time = 680 ns

Input

Output

high frequency continuous wave amplification

When presented with high frequency sinusoids in low-gain configurations (G < 5), the THS4601 experiences

a relatively large differential input voltage between the two input terminals of the amplifier. As this differential

input voltage increases, the internal slew-boosting circuitry can cause some transistors in the signal path to

enter the cutoff region of operation. As the derivative of the signal changes signs, these transistors suffer from

a short recovery time period, generating appreciable levels of distortion. This behavior is depicted in the graph

high-gain configurations including transimpedance applications, this phenomena is not problematic.

slew rate performance with varying input step amplitude and rise/fall time

Some FET input amplifiers exhibit the peculiar behavior of having a larger slew rate when presented with smaller

input voltage steps and slower edge rates due to a change in bias conditions in the input stage of the amplifier

under these circumstances. This phenomena is most commonly seen when FET input amplifiers are used as

voltage followers. As this behavior is typically undesirable, the THS4601 has been designed to avoid these

issues. Larger amplitudes lead to higher slew rates, as would be anticipated, and fast edges do not degrade

the slew rate of the device.