Capacitance measuring apparatus and capacitance measuring method

1. A capacitance measuring apparatus which comprises:

a voltage source for applying voltage fluctuation to a device under test;

an ammeter for measuring a leakage current flowing through the device under test before voltage fluctuation and the charging current flowing through the device under test as a result of voltage fluctuation; and

a current source for absorbing the leakage current so that the leakage current does not flow through the ammeter during voltage fluctuation.

2. The capacitance measuring apparatus according to claim 1 , wherein said current source is a floating current source wherein each terminal is connected to the respective terminal of the device under test.

3. The capacitance measuring apparatus according to claim 1 , wherein

said voltage source has means for measuring the applied voltage of the period when charging current flows through the device under test as a result of voltage fluctuation, and

further comprises an arithmetic part for calculating the leakage current value when the device under test is being charged based on the current measurement result of the ammeter and the voltage measurement result of the voltage source and calculating the capacitance value of the device under test using this leakage current value.

4. The capacitance measuring apparatus according to claim 1 , wherein

said device under test has a plurality of connection terminals;

the voltage source is connected to one of the connection terminals of the device under test; and

the current source and the ammeter are connected to the other connection terminal of the device under test.

5. The capacitance measuring apparatus according to claim 1 , further comprising a voltmeter; and wherein

said device under test has a plurality of connection terminals;

the voltmeter and the voltage source are connected in parallel to one of the connection terminals of the device under test; and

the current source and the ammeter are connected in parallel to the other connection terminal of the device under test.

6. The capacitance measuring apparatus according to claim 1 , further comprising a voltmeter; and wherein

said device under test has a plurality of connection terminals; the ammeter has two connection terminals and one of the connection terminals of said ammeter is connected to one of the connection terminals of the device under test;

the voltmeter and the voltage source are connected in parallel to the other connection terminals of said ammeter; and

the current source are connected to said one connection terminal of the device under test.

7. The capacitance measuring apparatus according to claim 2 , further comprising a voltmeter; and wherein

said device under test has a plurality of connection terminals;

the voltmeter and the voltage source are connected in parallel to one of the connection terminals of the device under test; and

the ammeter is connected to the other connection terminal of the device under test.

8. The capacitance measuring apparatus according to claim 2 , further comprising a voltmeter; and wherein

said device under test has a plurality of connection terminals;

the ammeter has two connection terminals and one of the connection terminals of said ammeter is connected to one of the connection terminals of the device under test; and

the voltmeter and the voltage source are connected in parallel to the other connection terminals of said ammeter.

9. A capacitance measuring method for measuring the capacitance of a device under test by the step voltage method, said capacitance measuring method comprises:

applying a voltage fluctuation via a voltage source to a device under test;

setting an output current value of a current source that absorbs the current flowing through a resistance component of the device under test to a value obtained by adding a measurement value of a leakage current one step before and an output current value of an ammeter one step before; and

measuring the leakage current flowing through the device under test before and after voltage fluctuation via an ammeter and a charging current flowing through the device under test as a result of voltage fluctuation.