In many studies of lightning flash characterization, the lightning generated electric field measuring system uses a circuit based on the buffer-amplifier LH0033. This circuit was proposed 35 years ago and there is no doubt of its excellent performance to measure the lightning electric field intensity. However, LH0033 is no longer manufactured, making it necessary to find a replacement. This paper proposes an improvement of the electric field measuring system, which consists of a new electronic circuit that uses the buffer-amplifier BUF602. This circuit presents a similar performance of the classic circuit, but has a lower energy consumption and allows its implementation in surface mount technology, which reduces the space required for the circuit. The field tests were performed in Bogotá, Colombia during a complete thunderstorm season and their results show that new circuit is a good alternative for measuring electric field signals with a bandwidth up to 11 MHz.