Data Sheet

ADHV4702-1

THEORY OF OPERATION

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Rev. D | 18 of 22

to reduce output stage peaking associated with capacitive loads.

CCOMP must be rated for the full supply differential. Figure 60 shows

the effect of CCOMP on various capacitive loads.

The values shown in Figure 58, Figure 59, and Figure 60 are

for unity gain configuration with a purely CLOAD. This is a worst

case scenario because the amplifier is more stable at higher gains

and with some resistive load in parallel with the load capacitance.

Although the RS or CCOMP significantly increases the stability while

driving CLOAD, they also reduce the headroom and bandwidth while

driving a resistive load. For resistive loads, leave the COMP pin

floating.

Figure 57. Circuit for CLOAD Drive

Figure 58. RS vs. CLOAD for Maximum 2 dB Peaking for Circuit from Figure 55,

TA = 25°C, AV = 1, VS = ±110 V, VOUT = 100 mV p-p, RF = 0 Ω, RADJ = 0 Ω

Figure 59. Small Signal Response for Various CLOAD and RS Values, TA =

25°C, AV = 1, VS = ±110 V, VOUT = 100 mV p-p, RF = 0 Ω, RADJ = 0 Ω

Figure 60. Small Signal Frequency Response vs. External Compensation, TA

= 25°C, AV = 1, VS = ±110 V, VOUT = 100 mV p-p, RF = 0 Ω, RADJ = 0 Ω

SAFE OPERATING AREA

The SOA represents the power handling capability of the device

under various conditions.

The power dissipation of the ADHV4702-1 occurs primarily from

the slew boosting circuit and output stage. The slew boosting

circuit requires additional supply current. Operating the amplifier

at its maximum slew rate at larger swing or at a high frequency

increases the current consumption of the slew boosting circuit,

increasing the TJ. Figure 61 shows the dynamic SOA that maintains

a TJ less than 150°C. The curve shows the maximum safe square

wave frequency for a given amplitude. Operating the ADHV4702-1

outside of the boundaries can cause permanent damage. Using ad-

ditional thermal management or input clamping diodes expands the

dynamic SOA significantly. However, using input clamping diodes

can compromise the slew rate and the large signal bandwidth.

The dc SOA is a curve of output current vs. the voltage across the

output stage, which is the voltage difference between supply and

output (VS − VOUT) under which the amplifier can operate at a safe

TJ. The areas under the curves of Figure 62 show the operational

boundaries of the ADHV4702-1 that maintain a TJ ≤ 150°C.

The SOA curves are unique to the conditions under which they

were developed, such as PCB, heat sink, and TA. All testing was

performed in a still air environment. Forced air convection in any of

the test cases effectively lowers θJA and expands the SOA.