Originally from SAE J1832 Nov 1989 - Gasoline Fuel Injector

Injector Driver—An electronic circuit that supplies voltage pulses to an electromagnetic fuel injector for a precise increment of time and at a given repetition rate. The accuracy of these pulses and their repetition is normally ±0.001 ms.
The peak-hold driver and the saturated driver are most commonly used by the industry for vehicle applications.

PEAK-HOLD DRIVER—A driver that uses two levels of current to operate the injector. The driver circuit applies battery voltage to the injector until a predetermined current level is reached. The current is then reduced and held at a lower level for the duration of the PW. This type of driver is normally used with injectors having low resistance coils (typically around 2 ohm). The accuracy of the driver peak current level (Ip) and the hold current level (Ih) is held to ±0.50%.

Advantages—The high peak current minimizes OT response and the low hold current minimizes CT response. This method of control results in an increased linear range of injector operation.

Disadvantages—Heat is primarily dissipated at the driver. Circuitry is more complex than that of the saturated driver.

SATURATED DRIVER—A power transistor driver that turns fully on for the entire duration of the injector PW. This type of driver is used with injectors having high resistance coils (typically 12 to 16 ohm) or with
injectors having low resistance coils in combination with a ballast resistor.

Advantages—Heat is primarily dissipated through the injector or ballast resistor and not at the driver circuit. Circuitry is simplified compared to the peak-hold driver.

Disadvantages—The inherently slower dynamic response of this system decreases the injector’s usable flow range. The Q of an injector used with this type of circuit is more duty cycle sensitive due to heat dissipation considerations. This driver’s inductive suppression, which may be resistance, capacitance or zener, significantly affects the injector’s Qd rates due to variations in the circuit’s current decay rate. This decay results in a change of the injector’s closing time.