Struct OtaRoot 

pub struct OtaRoot {
    pub model: OtaModel,
    /* private fields */
}

OTA nonlinear root for WDF trees.

Models the transconductance amplifier as a current-output device. The output current follows a tanh transfer characteristic: Iout = Iabc * tanh(Vin / (2*Vt))

The bias current Iabc controls the gain — this is the compression mechanism in OTA compressors. An envelope follower generates a control signal that reduces Iabc as the input gets louder, creating automatic gain reduction.

For the WDF constraint, the OTA output current flows through the load resistor, creating the voltage that the rest of the tree sees.

Fields

model: OtaModel

Implementations

impl OtaRoot

pub fn new(model: OtaModel) -> OtaRoot

pub fn set_iabc(&mut self, iabc: f64)

Set the amplifier bias current (external control from envelope, LFO, etc.).

In a compressor circuit, higher envelope = lower Iabc = less gain. Range: 0 to iabc_max.

pub fn iabc(&self) -> f64

Get current amplifier bias current.

pub fn set_gain_normalized(&mut self, gain: f64)

Set gain as a normalized value (0.0 = off, 1.0 = max gain).

This is a convenience wrapper for compressor-style control: the envelope follower output (0-1) directly maps to gain reduction.

pub fn output_current(&self, v_in: f64) -> f64

Compute the OTA output current for a given input voltage.

Uses the tanh transfer characteristic of the differential pair: Iout = Iabc * tanh(Vin / (2*Vt))

pub fn transconductance(&self) -> f64

Compute the transconductance (gm) at the current bias point.

gm = Iabc / (2 * Vt) — this is the small-signal gain. For CA3080 at Iabc=500µA: gm ≈ 9.7 mA/V (≈ 9.7 mS)

Trait Implementations

impl Clone for OtaRoot

fn clone(&self) -> OtaRoot

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for OtaRoot

impl Debug for OtaRoot

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl NlDeviceIv for OtaRoot

fn iv(&self, v: f64) -> (f64, f64)

OTA I-V characteristic for multi-NL MNA solver.

Returns (Iout, dIout/dVdiff) where:

• Iout = Iabc * tanh(v / (2*Vt))
• dIout/dVdiff = Iabc / (2*Vt) * sech²(v / (2*Vt))

fn v_clamp(&self) -> (f64, f64)

OTA differential input clamp: ±200mV (well beyond hard saturation at ~40mV).

impl WdfRoot for OtaRoot

fn process(&mut self, a: f64, rp: f64) -> f64

OTA transconductance: i = Iabc * tanh(v / (2·Vt))