Apparatus and methods for adjusting a gain of an electronic oscillator, such as a voltage-controlled oscillator (VCO), are disclosed. In one aspect, an apparatus for compensating for VCO gain variations includes a charge pump controller. The charge pump controller can be configured to select a VCO gain model based on a comparison of a VCO gain indicator and a threshold value stored in a memory, obtain VCO gain model parameters from the memory corresponding to the selected VCO gain model, and compute a charge pump current control value using the VCO gain model parameters. The charge pump current control value can be used to compensate for VCO gain variations.