Opamp (Operational Amplifier)

General Description

High level interface for interacting with the Operational Amplifier (Opamp).

Features

Each opamp can operate in one of two modes:

• Opamp: Bare opamp with two input pins.
• Follower: Also known as unity gain. Buffers the signal on a single input pin and drives the same voltage on the output.

In both modes, the output is driven off chip via another pin.

Quickstart

Call cyhal_opamp_init to initialize an opamp instance by providing the opamp object (obj), non-inverting input pin (vin_p), inverting input pin (vin_m), and output pin (vout). If follower mode is desired, pass NC for vin_m.

Use cyhal_opamp_set_power to configure the opamp power.

Code Snippets

Note

Error checking is omitted for clarity

Snippet 1: Bare opamp initialization

The following snippet initializes a bare opamp. Note that any passive components (e.g. resistive feedback) must be implemented off-chip.

    cy_rslt_t rslt;
    cyhal_opamp_t opamp_obj;

    /* Initialize opamp, using pin P9_0 for the non-inverting input, pin P9_1 for the inverting
     * input, and P9_2 for the output
     */
    rslt = cyhal_opamp_init(&opamp_obj, P9_0, P9_1, P9_2);

    /* Power on the opamp */
    rslt = cyhal_opamp_set_power(&opamp_obj, CYHAL_POWER_LEVEL_DEFAULT);

    /* Release opamp object after use */
    cyhal_opamp_free(&opamp_obj);

Snippet 2: Opamp follower initialization

The following snippet initializes an opamp as a follower.

    cy_rslt_t rslt;
    cyhal_opamp_t opamp_obj;

    /* Initialize opamp as follower, using pin P9_0 for the input and P9_2 for the output */
    rslt = cyhal_opamp_init(&opamp_obj, P9_0, NC, P9_2);

    /* Power on the opamp */
    rslt = cyhal_opamp_set_power(&opamp_obj, CYHAL_POWER_LEVEL_DEFAULT);

    /* Release opamp object after use */
    cyhal_opamp_free(&opamp_obj);

Snippet 3: Opamp powering-off and on

The following snippet demonstrates temporarily powering-off the opamp without freeing it.

    /* This assumes that the opamp has already been initialized as shown in snippet 1 or 2 */

    /* Power on the opamp */
    rslt = cyhal_opamp_set_power(&opamp_obj, CYHAL_POWER_LEVEL_DEFAULT);

    rslt = cyhal_opamp_set_power(&opamp_obj, CYHAL_POWER_LEVEL_OFF);

    /* When the opamp is needed again, power it back on */
    rslt = cyhal_opamp_set_power(&opamp_obj, CYHAL_POWER_LEVEL_DEFAULT);

API Reference
	Opamp HAL Results
	Opamp specific return codes.

Functions
cy_rslt_t	cyhal_opamp_init (cyhal_opamp_t *obj, cyhal_gpio_t vin_p, cyhal_gpio_t vin_m, cyhal_gpio_t vout)
	Initialize the opamp peripheral. More...
void	cyhal_opamp_free (cyhal_opamp_t *obj)
	Deinitialize the opamp peripheral and free associated resources. More...
cy_rslt_t	cyhal_opamp_set_power (cyhal_opamp_t *obj, cyhal_power_level_t power)
	Changes the current operating power level of the opamp. More...

Function Documentation

cyhal_opamp_init()

cy_rslt_t cyhal_opamp_init	(	cyhal_opamp_t *	obj,
		cyhal_gpio_t	vin_p,
		cyhal_gpio_t	vin_m,
		cyhal_gpio_t	vout
	)

Initialize the opamp peripheral.

If vin_m is NC, the opamp will be initialized in follower mode (unity gain).

The opamp will be initialized but not powered-on until cyhal_opamp_set_power is called.

Parameters

[out]	obj	Pointer to an opamp object. The caller must allocate the memory for this object but the init function will initialize its contents.
[in]	vin_p	Non-inverting input
[in]	vin_m	Inverting input
[in]	vout	opamp output

Returns

The status of the init request

cyhal_opamp_free()

void cyhal_opamp_free

(

cyhal_opamp_t *

obj

)

Deinitialize the opamp peripheral and free associated resources.

This will disconnect all inputs and outputs, including internal feedback.

Parameters

[in]

obj

The opamp object

cyhal_opamp_set_power()

cy_rslt_t cyhal_opamp_set_power	(	cyhal_opamp_t *	obj,
		cyhal_power_level_t	power
	)

Changes the current operating power level of the opamp.

If the power level is set to CYHAL_POWER_LEVEL_OFF, the opamp will be powered-off but it will retain its configuration, so it is not necessary to reconfigure it when changing the power level from CYHAL_POWER_LEVEL_OFF to any other value.

Parameters

[in]	obj	Opamp object
[in]	power	The power level to set

Returns

The status of the set power request