Voltage sampling circuits

A voltage sampling circuit arrangement comprising:

• an oscillator circuit portion arranged to produce a periodic oscillator output signal at an oscillation frequency dependent on a bias current provided thereto;
• a sampling circuit portion arranged selectively to connect an input terminal to an output terminal in response to an applied switching signal derived from said oscillator output signal, wherein said sampling circuit portion comprises a sampling transistor which has a current leakage dependent on temperature;
• and
• a biasing circuit portion arranged to provide said bias current to the oscillator circuit portion wherein said bias current is dependent on temperature and wherein said biasing circuit portion comprises;
• a leakage transistor matched to the sampling transistor such that when a leakage current flows through the sampling transistor, a similar current will flow through the leakage transistor;
• and
• a constant current source arranged to provide a constant current that is substantially independent of temperature;
• wherein
• the biasing circuit portion is arranged to sum the constant current provided by the constant current source with the additional bias current provided by the leakage transistor, such that the frequency of the oscillator circuit portion will only rise above a minimum oscillation frequency when the circuit is experiencing an elevated temperature.