PIC16F753 datasheet(132/230 Pages) MICROCHIP

132 / 230 page

PIC16F753/HV753

DS40001709C-page 132

 2013-2015 Microchip Technology Inc.

16.0

OPERATIONAL AMPLIFIER

(OPA) MODULE

The Operational Amplifier (OPA) is a standard three-

terminal device requiring external feedback to operate.

The OPA module has the following features:

• External Connections to I/O Ports

• Selectable Unity Gain Bandwidth Product Option

• Low Leakage Inputs

• Factory Calibrated Input Offset Voltage

16.1

OPAxCON0 Register

The OPAxCON0 register, shown in Register 16-1,

controls the OPA module.

The OPA module is enabled by setting the OPAxEN bit

of the OPAxCON register. When enabled, the OPA

forces the output driver of the OPAxOUT pin into tri-

state to prevent contention between the driver and the

OPA output.

The OPAxUGM bit of the OPAxCON register enables

the Unity Gain Bandwidth mode (voltage follower) of

the amplifier. In Unity Gain mode, the OPAxNCH<1:0>

inputs are disabled. The default mode is normal three-

terminal operation.

16.2

Effects of a Reset

A device Reset forces all registers to their Reset state.

This disables the OPA module.

16.3

OPA Module Performance

Common AC and DC performance specifications for

the OPA module:

• Common Mode Voltage Range

• Leakage Current

• Input Offset Voltage

• Open Loop Gain

• Gain Bandwidth Product

Common mode voltage range is the specified voltage

range for the OPAx+ and OPAx- inputs, for which the

OPA module will perform within its specifications. The

OPA module is designed to operate with input voltages

between VSS and VDD. Behavior for Common mode

voltages greater than VDD or below VSS is not

guaranteed.

Leakage current is a measure of the small source or

sink currents on the OPAx+ and OPAx- inputs. To

minimize the effect of leakage currents, the effective

impedances connected to the OPAx+ and OPAx- inputs

should be kept as small as possible and equal. Input

offset voltage is a measure of the voltage difference

between the OPAx+ and OPAx- inputs in a closed loop

circuit with the OPA in its linear region. The offset

voltage will appear as a DC offset in the output equal to

the input offset voltage, multiplied by the gain of the

circuit.

The input offset voltage is also affected by the Common

mode voltage. The OPA is factory-calibrated to

minimize the input offset voltage of the module. Open

loop gain is the ratio of the output voltage to the

differential input voltage (OPAx+) - (OPAx-). The gain is

greatest at DC and falls off with frequency.

Gain Bandwidth Product or GBWP is the frequency at

which the open loop gain falls off to 0 dB. The lower

GBWP is optimized for systems requiring low-fre-

quency response and low-power consumption.

Note:

When the OPA module is enabled, the

OPAxOUT pin is driven by the op amp

output, not by the PORT digital driver.

Refer

Section 22.0

“Electrical

Specifications” for the op amp output

drive capability.

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