OPA835 datasheet(9/21 Pages) TI1

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-2.5 V

Load

VOUT

+2.5 V

½ OPA2834

VSIG

VIN

5 k

VOUT

½ O PA283 4

VIN

5 k

VOUT

½ O PA283 4

OPA2834

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SBOS973 – JUNE 2019

Product Folder Links: OPA2834

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Feature Description (continued)

As expected, larger value gain resistors cause lower bandwidth and peaking in the response (peaking in the

frequency response is synonymous with overshoot and ringing in the pulse response). Adding 1-pF capacitors in

parallel with RF helps compensate the phase margin and restores flat frequency response. Figure 4 shows the

test circuit.

Figure 4. G = 2 Test Circuit for Various Gain-Setting Resistor Values

8.3.4 Driving Capacitive Loads

The OPA2834 drives up to a nominal capacitive load of 10 pF on the output with no special consideration. When

driving capacitive loads greater than 10 pF, TI recommends using a small resistor (RO) in series with the output

as close to the device as possible. Without RO, output capacitance interacts with the output impedance of the

amplifier causing phase shift in the loop gain of the amplifier that reduces the phase margin. This reduction in the

phase margin causes peaking in the frequency response and overshoot and ringing in the pulse response.

Interaction with other parasitic elements can lead to instability or oscillation. Inserting RO isolates the phase shift

from the loop gain path and restores the phase margin; however RO can limit the bandwidth slightly. Figure 5

shows a diagram of driving capacitive loads.

Figure 5. Driving Capacitive Loads With the OPA2834

8.4 Device Functional Modes

8.4.1 Split-Supply Operation (±1.35 V to ±2.7 V)

To facilitate testing with common lab equipment, the OPA2834EVM (see the OPA2837DGK Evaluation Module

user guide) is built to allow split-supply operation. This configuration eases lab testing because the mid-point

between the power rails is ground, and most signal generators, network analyzers, oscilloscopes, spectrum

analyzers, and other lab equipment have inputs and outputs with a ground reference.

Figure 6 shows a simple noninverting configuration analogous to Figure 1 with a ±2.5-V supply and VREF equal to

ground. The input and output swing symmetrically around ground. For ease of use, split supplies are preferred in

systems where signals swing around ground.

Figure 6. Split-Supply Operation

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