Opamp (Operational Amplifier)

group group_hal_opamp

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);

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.

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.

Return

The status of the init request

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

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

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.

Return

The status of the set power request

Parameters

  • [in] obj: Opamp object

  • [in] power: The power level to set