Preamplifier for digital phosphor oscilloscope

The invention provides a 1.5GHz preamplifier for a digital phosphor oscilloscope. The preamplifier comprises a high-resistance attenuator, an impedance transformer, a low-resistance step programmable attenuator, a high-speed differential amplifier, a high and low resistance selector and the like. High and low resistance are selected for an input signal; when the low resistance is selected, the signal passes through a radio frequency relay and directly enters the low-resistance step programmable attenuator; and when the high resistance is selected, the signal passes through the high-resistance attenuator and an impedance transformation circuit, is converted from high-resistance input to low-resistance output, and then enters the low-resistance step programmable attenuator through a radio frequency two-way selective switch, and the tasks of performing fine gain tuning, converting a single-ended signal into a differential signal and performing level conversion are finished by using the high-speed differential am