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Ground near the op amp - is it ok?

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Su Ram

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If ground plane is close to the op amp pins, does it affect the input noise or anyother parameter of the amplifier?
 

Rame

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Hi,

A ground plane acts as a common reference voltage, provides shielding, enables heat dissipation, and reduces stray inductance (but it also increases parasitic capacitance). While there are many advantages to using a ground plane, care must be taken when implementing it, because there are limitations to what it can and cannot do.

High-speed op amps will perform better if the ground plane is removed from under the input and output pads. The stray capacitance introduced by the ground plane at the input, added to the op amp’s input capacitance, lowers the phase margin and can cause instability to the circuit.

Analog and digital circuitry, including grounds and ground planes, should be kept separate when possible. Fast-rising edges create current spikes flowing in the ground plane. These fast current spikes create noise that can corrupt analog performance. Analog and digital grounds (and supplies) should be tied at one common ground point to minimize circulating digital and analog ground currents and noise.


Hope this helps you....




Regards,


Ramesh
 

Su Ram

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Thanks for that..I have coplanar transmission lines as inputs to the op amp pin.. Do you know if the grounds on it also affect?
 

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