Bidirectional I2C Level Shifter

In some cases I2C signals need to be level-converted if they are exchanged between (sections of) logic systems operating at different supply voltages. For example, one section of a circuit may work at 5 V while a newly added I2C device is happy at just 3.3 V. Without a suitable bidirectional level converter, signals from the 5-V system may disrupt or even damage the SDA/SCL inputs of the 3.3-V device, while the other way around signals emitted by the lower voltage device may not be properly detected.