| 摘要 |
PROBLEM TO BE SOLVED: To provide a print head drive circuit capable of reducing distortion in the output waveform from a current amplification circuit in case of a light load. SOLUTION: The output waveform from (the charging circuit of) a current amplification circuit 5 changes with an intermediate potential (e.g. about 20 V) until the time T<SB>1</SB>when the base-emitter voltage (Vbe<SB>1</SB>) of a TR9, i.e. the first stage TR, reaches 0.7 V, as shown by a dashed line 25. When the Vbe<SB>1</SB>reaches 0.7 V at the time T<SB>1</SB>, a TR11 is conducted (turned on) and since the resistance of a resistor 17 is sufficiently lower than the impedance of the TR11 under nonconducting state (turn off), a current flows from V<SB>DD</SB>to a drive current transmission line 21 through the TR11 and the resistor 17. Consequently, the waveform of the output voltage rises substantially vertically and then increases with a predetermined gradient to a target level. COPYRIGHT: (C)2005,JPO&NCIPI
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