Electrostatic discharge protection circuit

An ESD protection circuit for protecting a core circuit, comprising:

• a first HEMT coupled to a first input terminal;
• a second HEMT coupled between the first HEMT and a second input terminal;
• a first current clamping circuit coupled between the second input terminal and a gate of the second HEMT, and comprising:
• a third HEMT comprising a drain, a source, and a gate;
• a second current clamping circuit coupled between the first input terminal and a gate of the first HEMT;
• and
• a first resistor coupled between the first input terminal and the core circuit,
• wherein:
• the drain and the source of the third HEMT are coupled to the second input terminal, and the gate of the third HEMT is coupled to the gate of the second HEMT, and
• the size of the first HEMT or the second HEMT is larger than the size of the third HEMT.

An ESD protection circuit for protecting a core circuit, comprising:

• an enhancement-mode HEMT coupled to the core circuit in parallel;
• a first HEMT coupled to a first input terminal;
• a second HEMT coupled to the first HEMT and a second input terminal;
• a first current clamping circuit comprising:
• a third HEMT coupled to the first input terminal and a gate of the second HEMT;
• and
• a first resistor coupled to the first input terminal and a gate of the enhancement-mode HEMT,
• wherein the enhancement-mode HEMT is coupled to the second input terminal and a third input terminal, and the size of the first HEMT or the second HEMT is larger than the size of the third HEMT.