1.6MHz Bandwidth, Low Noise Precision Op‐amps

www.3peakic.com

Rev. A

1. For Non-Inverting Gain and Unity-Gain Buffer:

2. For Inverting Gain and Trans-impedance Gain Amplifiers (convert current to voltage, such as photo detectors):

 

Figure 6 The Layout of Guard Ring

Power Supply Layout and Bypass

0.01μF to 0.1μF) within 2mm for good high frequency performance. It can also use a bulk capacitor (i.e., 1μF or larger)

within 100mm to provide large, slow currents. This bulk capacitor can be shared with other analog parts.

Ground layout improves performance by decreasing the amount of stray capacitance and noise at the OPA’s inputs

and outputs. To decrease stray capacitance, minimize PC board lengths and resistor leads, and place external

components as close to the op amps’ pins as possible.

Proper Board Layout

To ensure optimum performance at the PCB level, care must be taken in the design of the board layout. To avoid

leakage currents, the surface of the board should be kept clean and free of moisture. Coating the surface creates a

barrier to moisture accumulation and helps reduce parasitic resistance on the board.

Keeping supply traces short and properly bypassing the power supplies minimizes power supply disturbances due to

output current variation, such as when driving an ac signal into a heavy load. Bypass capacitors should be connected

as closely as possible to the device supply pins. Stray capacitances are a concern at the outputs and the inputs of the

amplifier. It is recommended that signal traces be kept at least 5mm from supply lines to minimize coupling.

A variation in temperature across the PCB can cause a mismatch in the Seebeck voltages at solder joints and other

points where dissimilar metals are in contact, resulting in thermal voltage errors. To minimize these thermocouple

effects, orient resistors so heat sources warm both ends equally. Input signal paths should contain matching numbers

and types of components, where possible to match the number and type of thermocouple junctions. For example,

dummy components such as zero value resistors can be used to match real resistors in the opposite input path.

Matching components should be located in close proximity and should be oriented in the same manner. Ensure leads

are of equal length so that thermal conduction is in equilibrium. Keep heat sources on the PCB as far away from

amplifier input circuitry as is practical.

The use of a ground plane is highly recommended. A ground plane reduces EMI noise and also helps to maintain a

constant temperature across the circuit board.