Low voltage circuit with variable substrate bias

A circuit comprising a bias stage having an input signal terminal for receiving an input signal, the circuit modifying the input signal with a drive stage to provide an output signal in complement form, comprising:

• a load;
• a drive transistor in the drive stage of the circuit, the drive transistor having a bulk connected to a terminal of the load and a control electrode coupled to the input signal terminal;
• and
• a bias transistor in the bias stage of the circuit, the bias transistor having a bulk that is directly connected to the terminal of the load and to the bulk of the drive transistor, the bias transistor having a control electrode coupled to the input signal terminal, the bias transistor having a current electrode directly connected to both the terminal of the load and to the bulk of the bias transistor, wherein voltage applied to the bulk of the drive transistor and the bulk of the bias transistor varies in response to the input signal.

A circuit comprising:

• a load having a first terminal coupled to a first voltage terminal and having a second terminal;
• a first transistor having a control electrode coupled to an input signal terminal, a first current electrode coupled to a complementary output terminal and both a second current electrode and a bulk connected together and to the second terminal of the load;
• a second transistor having a control electrode coupled to the input signal terminal, a first current electrode coupled to the first voltage terminal, a second current electrode coupled to the complementary output terminal, and a bulk connected to the bulk of the first transistor;
• and
• a pull-up transistor coupled in series with the second transistor, said pull-up transistor located between a second voltage terminal and the complementary output terminal.