Multi-level pulser and related apparatus and methods

1. An apparatus, comprising:

at least one ultrasonic transducer on a first substrate; and

a multi-level pulser on a second substrate coupled to the at least one ultrasonic transducer, wherein the first substrate and the second substrate are different substrates, the multi-level pulser including:

a plurality of input terminals configured to receive respective input voltages;

an output terminal configured to provide an output voltage; and

a signal path between a first input terminal of the plurality of input terminals and the output terminal including a first transistor coupled to a first diode and, in parallel, a second transistor coupled to a second diode,

wherein the first transistor is either a pMOS transistor or an nMOS transistor and the second transistor is an NMOS transistor if the first transistor is a pMOS transistor or a pMOS transistor if the first transistor is an nMOS transistor.

2. The apparatus of claim 1 , further comprising a controller configured to control a charge and discharge of an output capacitance associated with the ultrasonic transducer so as to provide charge recycling.

3. The apparatus of claim 1 , wherein the multi-level pulser comprises a plurality of signal paths between respective input terminals of the plurality of input terminals and the output terminal, each signal path including a pMOS or nMOS transistor coupled to a first diode and, in parallel, a pMOS or nMOS transistor coupled to a second diode, wherein the pMOS or nMOS transistor coupled to the second diode is an nMOS transistor when the pMOS or nMOS transistor coupled to the first diode is a pMOS transistor, and wherein the pMOS or nMOS transistor coupled to the second diode is a pMOS transistor when the pMOS or nMOS transistor coupled to the first diode is an nMOS transistor.

4. The apparatus of claim 1 , wherein the output voltage is equal to a predetermined input voltage.

5. The apparatus of claim 1 , further comprising a capacitor coupled to the output terminal.

6. The apparatus of claim 1 , further comprising a resistor coupled to the output terminal.

7. The apparatus of claim 1 , wherein the first transistor is pMOS and the second transistor is nMOS.

8. The apparatus of claim 1 , wherein the first diode has an anode connected to the first transistor and a cathode connected to the output terminal.

9. The apparatus of claim 1 , wherein the second diode has a cathode connected to the second transistor and an anode connected to the output terminal.

10. An apparatus, comprising:

at least one ultrasonic transducer on a first substrate, and a level shifter on a second substrate coupled to the at least one ultrasonic transducer, wherein the first substrate and the second substrate are different substrates, the level shifter including:

an input terminal configured to receive an input voltage;

an output terminal configured to provide an output voltage level-shifted from the input voltage;

a capacitor coupled between the input terminal and the output terminal; and

a diode coupled in a reverse-biased configuration between an input to an active high voltage element and a first voltage of a high voltage power supply;

wherein the input of the active high voltage element is coupled to an output of the capacitor.

11. The apparatus of claim 10 , wherein the first substrate is a semiconductor substrate.

12. The apparatus of claim 10 , wherein the at least one ultrasonic transducer is a capacitive micromachined ultrasonic transducer (CMUT).

13. The apparatus of claim 10 , further comprising a pulser on the second substrate and coupled to the level shifter.

14. The apparatus of claim 10 , comprising a plurality of ultrasonic transducers including the at least one ultrasonic transducer, wherein the plurality of ultrasonic transducer are configured to apply high intensity focused ultrasound (HIFU).