2. Minimize the distance (less than 0.25-in) from the power-supply pins to high-frequency decoupling

capacitors. Use high quality, 100-pF to 0.1-µF, C0G and NPO-type decoupling capacitors with voltage

ratings at least three times greater than the amplifiers maximum power supplies to ensure that there is a

low-impedance path to the amplifiers power-supply pins across the amplifiers gain bandwidth specification.

At the device pins, do not allow the ground and power plane layout to be in close proximity to the signal I/O

pins. Avoid narrow power and ground traces to minimize inductance between the pins and the decoupling

capacitors. The power-supply connections must always be decoupled with these capacitors. Larger (2.2-µF

to 6.8-µF) decoupling capacitors, effective at lower frequency, must be used on the supply pins. These are

placed further from the device and are shared among several devices in the same area of the PC board.

3. Careful selection and placement of external components will preserve the high frequency

performance of the OPA817. Use low-reactance resistors. Surface-mount resistors work best and allow

a tighter overall layout. Never use wirewound type resistors in a high frequency application. Because the

output pin and inverting input pin are the most sensitive to parasitic capacitance, always position the

feedback and series output resistor, if any, as close as possible to the inverting input and the output pin,

respectively. Other network components, such as noninverting input termination resistors, should also be

placed close to the package. Even with a low parasitic capacitance at the noninverting input, high external

resistor values can create significant time constants that can degrade performance. When OPA817 is

configured as a conventional voltage amplifier, keep the resistor values as low as possible and consistent

with the load driving considerations. Decreasing the resistor values keeps the resistor noise terms low and

minimizes the effect of the parasitic capacitance. However, lower resistor values increase the dynamic power

4. Heat dissipation is important for a high voltage device like OPA817. For good thermal relief, the thermal

pad should be connected to a heat spreading plane that is preferably on the same layer as OPA817 or

connected by as many vias as possible, if the plane is on a different layer. It is recommended to have at

least one heat spreading plane on the same layer as the OPA817 that makes a direct connection to the

thermal pad with wide metal for good thermal conduction when operating at high ambient temperatures. If

more than one heat spreading plane is available, then connect them by a number of vias to further improve

the thermal conduction.

11.1.1 Thermal Considerations

The OPA817 will not require heatsinking or airflow in most applications. Maximum allowed junction temperature

will set the maximum allowed internal power dissipation as described in the following paragraph. In no case

should the maximum junction temperature be allowed to exceed 150°C.

when the output is fixed at a voltage equal to 1/2 of either supply voltage (for balanced bipolar supplies). Under

Note that it is the power in the output stage and not into the load that determines internal power dissipation.

maximum specified ambient temperature of +105°C and driving a grounded 100-Ω load.

All actual applications will be operating at lower internal power and junction temperature.

OPA817

SBOS847 – JULY 2022

www.ti.com

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